Since the 1970s the American political system has undergone a dramatic increase in partisan polarization. By polarization, we mean that the parties are “far apart” from each other. This is largely, but not exclusively, a matter of policy views, although it may include important elements of identity-based tribalism. In a highly polarized environment, parties view one another as competing camps engaged in a battle where the stakes attached to victory or defeat are extremely high.

Scholars have a growing understanding of some of the forces that fostered this high-polarization setting and have begun to advance our understanding of many of its characteristics as well.Footnote ¹ Yet we are just beginning to wrestle effectively with the profound consequences of modern polarization for our politics. In this chapter, we explore some aspects of how that polarization is influencing executive-legislative relations, a potentially vital domain for democratic resilience. We devote considerable attention, however, to specifying some of the broader elements of this reconfigured polity, because we consider this essential to explaining why executive-legislative relations no longer work the way they once did.

Much of the literature on today’s polarized system has been fairly reassuring, suggesting that an extended period of polarization – which now spans at least a quarter-century – reaffirms the flexibility of our Madisonian framework. A number of propositions bolster this position, ranging from the assertion that American politics has often been equally polarized in the past to the claim that partisan tactical battles in a closely divided Congress greatly accentuate the divisions seen in congressional roll-call votes, which are usually interpreted solely as evidence of deep ideological polarization.Footnote ²

In recent work we have raised doubts about this assessment.Footnote ³ Adopting a developmental approach to polarization, we investigate how broad institutional configurations, extending beyond formal political institutions, might either dampen or intensify polarization once it emerges. From this perspective, contemporary polarization looks quite distinctive. In past eras, what we term meso-institutions – systems of interest intermediation, state parties operating within a geographically extensive and decentralized federal polity, and the ecology of news media – typically acted as important countervailing mechanisms. By fostering robust factional divisions in the parties, they repeatedly constrained or undermined polarization. The polarization that developed over the past generation, by contrast, has altered this meso-institutional landscape. It has encouraged the rise of new organizations and transformed existing ones, creating new relationships, balances of political power, and incentives. These changes, in turn, have generally discouraged the activation of divisions within the parties while intensifying the divisions between the parties, their supporting coalitions, and voters.Footnote ⁴ In short, many of the self-correcting mechanisms of the Madisonian polity so often celebrated in the past have either weakened or themselves been transformed into engines of polarization. At the same time, these changes have had large effects on the workings of formal institutions. By undercutting the separation of political incentives necessary to make a separation-of-powers system robust, the rise of intense polarization dividing two increasingly coherent and cohesive political teams introduces new instabilities into the American political system. We argue that these changes in meso-institutions are particularly acute on the right, with important implications for the robustness of American democratic institutions.

The Madisonian System: A Shield against Extreme Polarization?

Briefly connecting our arguments about the intensification of polarization explicitly to the structure of American political institutions can clarify the potential impact on critical dimensions of governance. The standard, Madisonian account of American politics emphasizes the ways in which core political institutions encourage compromise and stability. The Founders were, of course, preoccupied with the question of how to create a stable republic. Understanding that factional divisions are inevitable, Madison famously argued that American political institutions could prevent all-out conflict between competing camps. Critical mechanisms that would tend to attenuate or countervail against polarization, rather than reinforce it, were built directly into the constitutional system. Others, such as the development of what were by comparative standards highly decentralized and geographically factionalized political parties, were crucial (if unintended) outgrowths of the constitutional framework.

Most obviously, separation of powers, checks and balances, and federalism divide power, making it less likely that any single group will gain control of the entire government. This, in turn, means that governance will routinely require accommodating a range of group interests. The rules structuring elections require the assembly of different kinds of coalitions for different offices, discouraging the emergence of a single coherent and dominant cleavage. The creation of an extended republic with immense geographic diversity reinforced the institutional obstacles to polarization. Madison lays out the logic of this argument in Federalist 10: The scope of the new nation implied a diversity of viewpoints, which would make the emergence of a majority faction unlikely.Footnote ⁵ Creating a majority would require broad appeals to widely shared interests, rather than narrow, parochial appeals to a particular faction. As Dahl and Lindblom argue, social pluralism, when combined with America’s fragmented constitutional structure, forces bargaining among diverse groups in order to achieve policy success.Footnote ⁶

Federalism, from this perspective, interacts with the extended republic in critical ways. It is not just that the national government shares power with fifty separate state governments: The diversity of state circumstances and the relative autonomy of state political institutions together foster the emergence and sustenance of a diversity of interests and groups. This, too, promotes carefully brokered compromises that are mindful of an array of distinctive interests.Footnote ⁷

These core institutions of American government tend to frustrate efforts of a particular coalition or individual to consolidate power. Crucially, it is not just that the division of authority encourages a search for broad consensus that can accommodate opposing interests. In addition, the allocation of authority to distinct, geographically organized representatives actively encourages the generation and maintenance of diverse interests. Moreover, under many conditions, we can think of these institutional arrangements as functionally equivalent mechanisms for attenuating polarization. Even if one mechanism weakens in a particular context – such as when unified government reduces Congress’s incentive to check the president – there are built-in redundancies that reinforce the overall tendency toward stability and moderation. Finally, these institutional arrangements have a homeostatic quality. Given the diversity of interests, and the independence and diversity of political settings and roles, politicians unwilling to engage in compromise are likely to face increasing resistance.

The American constitution left a powerful mark on American political parties, rendering them unlikely vessels for intensely and durably polarized politics. From the start, American political institutions helped produce parties that were federal in character and decentralized in many of their operations.Footnote ⁸ In the words of V. O. Key, American parties were “confederative,” consisting “of a working coalition of state and local parties” that provided pluralistic representation of diverse interests.Footnote ⁹ A critical source of power and independence for state parties has been their control of nominations and, more generally, their role in shaping career paths for ambitious politicians. Truman observes that “the basic political fact of federalism is that it creates separate, self-sustaining centers of power, privilege, and profit … [and] bases from which individuals may move to places of greater influence and prestige in and out of government.”Footnote ¹⁰ Polsby, echoing an earlier comment from Dwight Eisenhower, argues that “one may be justified in referring to the American two-party system as masking something more like a hundred-party system.”Footnote ¹¹ A Massachusetts Democrat and an Alabama Democrat might belong to the same formal organization at the national level, but they need not agree on much of anything when it comes to policy. Hershey, in her textbook on American parties, concludes that federalism and separation of powers mean that American legislative parties “can rarely achieve the degree of party discipline that is common in parliamentary systems.”Footnote ¹²

This feature of party politics lowered the stakes of political conflict – an effect that comparativists have long stressed is conducive to democratic stability.Footnote ¹³ Even if one party wins power, it is forced to accommodate a diverse array of interests that likely will make its ultimate policies broadly acceptable. Furthermore, the crosscutting cleavages and fluidity of alliances ensure that even if one’s side loses today, the outcome could easily change soon.Footnote ¹⁴ The operations of the constitutional system might be remade on the ground over time by assertive presidents or new ideological formations (e.g., the New Deal), but the core features that gave rise to pluralism and fragmented power remained: separation of powers, checks and balances, territorially grounded representation, and the extended republic.Footnote ¹⁵ The modern presidency is a much more powerful office than Madison anticipated, yet modern presidents continued to be frustrated by the need to deal with contending power centers in Congress, the Courts, the bureaucracy, and the states.Footnote ¹⁶ The New Deal remade the role of the national government, yet also had to confront fundamental limitations imposed by separation of powers, federalism, and the Democrats’ north–south regional coalition.Footnote ¹⁷

In summary, while political parties might bridge the differences across branches, institutions, or localities in a way that the Framers had not anticipated, sustained, intense policy polarization at the national level has been rare. Even in periods of high party voting in Congress, substantial intraparty divisions limited the scope of partisan battles. A fragmented party and interest group system meant that national party lines failed to capture or contain many of the critical disputes animating politics. Because this system created institutional spaces within which these divisions could operate and shape the incentives of important political actors, they countered the force of national party polarization. For all of its acute limitations, the Madisonian system was, for much of American history, a robust obstacle to narrow and durable consolidations of power.

It bears emphasis that comparativists, concerned about the stability of democracy and that of presidential systems in particular, have also noted the impact of these unusual institutional arrangements. Linz argues that presidential systems tend to be less stable due to dueling bases of legitimacy.Footnote ¹⁸ Viewing the United States as an exception, Linz suggests that our weak and fragmented parties have prevented this kind of all-or-nothing showdown between branches under the control of competing parties. We argue below that this confidence in the moderating influence of American political institutions may no longer be justified. Moreover, the particular perils Linz associates with presidentialism might obscure several different challenges for democracy associated with intensifying polarization within a Madisonian framework. First, however, we briefly describe how the transformation of “meso-institutions” of interest intermediation, state parties, and media has contributed to the reconfiguration of the American polity.

Modern Polarization and the Remaking of Meso-institutions

The initial development of modern polarization had profound consequences for the American polity. Standard accounts of its emergence emphasize the sorting of the parties, at both the elite and mass levels, which flowed from realignment of the political parties around issues of race.Footnote ¹⁹ In this necessarily abbreviated account, we do not challenge that basic depiction, but wish to stress that the initial rise in polarization – against a backdrop of technological change and a vastly expanded role of the federal government – helped to transform what we call meso-institutions: interest groups, state parties, and the media. In earlier eras, these arrangements had been crucial bulwarks of the formal institutions of our Madisonian system, tending to attenuate partisan polarization. Today, they instead encourage further national party polarization.Footnote ²⁰

We briefly recap the analysis we have offered of interest groups, state parties, and media.Footnote ²¹ Traditionally, American political structures encouraged a diffuse and fluid structure of interest intermediation – interest group structures were both unusually fragmented, and only weakly aligned with national parties.Footnote ²² Growing polarization (intersecting in important ways with the expanding role of the national government during what Skocpol has called “the long-1960s”) led to a proliferation and nationalization of interest group activity (Skocpol 2003). Over time, the new environment produced a second major shift: a growing inclination of powerful groups to align with a party – to try to achieve their policy goals by working with, and in support of, a durable political coalition (Pierson 2014; Krimmel 2017). Rather than being a source of incentives and action that crosscut parties and thus restricted polarization, interest groups became yet another factor reinforcing the divide between them. A powerful self-reinforcing logic was at play. As a party moves closer to an interest group’s preferred policy positions (and the other party moves in the opposite direction), the stakes in the outcome of interparty conflict increase. As groups join teams, see increasing benefits of victory by their team, and thus work to ensure those victories while punishing defectors, interest group political behavior can intensify polarization rather than moderating it.

Indeed, the transformed interplay between groups and parties does more than just remove one of the traditional mechanisms that limit polarization. Many of these contemporary groups are national in scope and invested in an ambitious policy agenda. They eagerly push their partisan allies to advance that agenda wherever possible, helping to pull state parties more tightly into this nationalized system (Hertel-Fernandez 2020).Footnote ²³ Parties have contracted out mobilizing voters to groups, which may also have considerable influence over fundraising and candidate recruitment. The fixation on winning elections that characterized many traditional party elites encouraged moderation. Party networks, however, increasingly lack the kind of robust organizational infrastructure that might limit extremism. Under conditions of polarization, they may cede power to groups whose strategies of organizational maintenance often rely on extreme appeals and who may be more accepting of electoral risk to achieve potentially extreme ends (Azari 2018).Footnote ²⁴

This dynamic of intensifying partisan polarization and weakening of crosscutting cleavages is equally evident in state parties. For much of its history, America’s federal party system tended to act as a countervailing mechanism limiting partisan polarization. Even when the national parties were relatively polarized on a given set of issues – such as the tariff in the late nineteenth century – state and local parties provided a partially independent, geographically rooted power base to represent competing interests that crosscut that division. Perhaps even more important, the geographically decentralized party system provided a mechanism to incorporate new interests that fit uncomfortably with existing national party coalitions. National parties lacked a veto over state party positions. Nor did they have any effective way of preventing the entry of new groups into a state party coalition, even when those positions and groups undermined an existing line of cleavage. This process of geographically rooted factional entry repeatedly drove change in partisan alignments and coalitions.Footnote ²⁵

It is far more difficult for today’s state parties to play this countervailing role. They are more tightly integrated into national party networks. Key resources are outside the control of state party leaders. National party organizations have become more active as a source of funds and professional services for local candidates, encouraging greater coordination across states (Lunch 1987, Paddock 2015). Nomination process reforms that empower ordinary voters have also shifted influence within states from professional, locally rooted politicians to policy-oriented activists who often focus on hot-button issues that divide the parties nationally (La Raja & Schaffner 2015).Footnote ²⁶ Meanwhile, fundraising has been nationalized. Drawing on Federal Election Commission data, Hopkins finds that the share of itemized campaign contributions that cross state lines increased from 31 percent in 1990 to 68 percent in 2012.Footnote ²⁷ The nationalization of politics, including of communication networks, has made it harder for state parties and politicians to tailor their identity to local conditions. As Hopkins notes, “state parties themselves … especially as voters perceive them, have increasingly come to mirror their national counterparts.”Footnote ²⁸

As with the transformed role of interest groups, these changes in state party politics help make polarization self-reinforcing. When it becomes harder for state politicians to distinguish themselves from the national party brand in the eyes of voters, their incentives change. As Hopkins puts it, state politicians “may well come to see their ambitions as tethered more closely to their status in the national party than their ability to cater to the state’s median voter.”Footnote ²⁹ When an issue potentially separates the state’s median voter from the position of the national party, politicians’ incentives to toe the national party line have grown stronger, as voters prove less attentive to state-level differences and as the relevant audience for their behavior (interest groups, donors, etc.) becomes more nationalized. The result is a more integrated party system. What were once relatively autonomous state and local party organizations that provided a basis for dissident factions to form and challenge national party lines now appear to be “rather small cogs” in a nationally oriented network.Footnote ³⁰ Within this new, more integrated system, state-level politicians find it in their interest to reinforce or even intensify existing national alignments.

Federalism has become, increasingly, yet another arena and instrument of national party competition. State party actors now use their power – particularly under conditions of unified control – to pursue policies that are in line with their national party’s agenda, and, at times, to shape the electoral rules of the game in ways that boost the national party’s chances (see Hertel-Fernandez, this volume, and Rocco, this volume).Footnote ³¹ A state under the control of the party opposing the president – Texas in the Obama years or California in the Trump years – can serve as an important power base challenging national-level policies, at times uniting with other states of a similar partisan complexion to forge a new front in policy battles. But in doing so, these states reinforce, rather than undermine, the intense national party divide.

Media represents a third “meso-institution” that once helped to limit polarization but now intensifies it. The presence of partisan or ideological news outlets is nothing new in American history. But the party press of the nineteenth century was not nationalized. Although more research is required on this topic, case study evidence suggests that voters in different regions who belonged to the same party did not necessarily receive the same messages about key issues. For example, as the fifty-first Congress debated the tariff and currency in 1890, GOP newspapers were divided regionally and thus provided a crosscutting set of cues for many voters as well as local political elites.Footnote ³²

Technological and commercial developments, such as the rise of cable news, talk radio, and social media, have created a much more nationalized media infrastructure, diminishing the role of locally grounded information and issues. These trends have also fueled the growth of an “outrage industry,” especially on the political right, that is increasingly geared to partisans.Footnote ³³ This industry has powerful incentives to intensify polarization in two respects. First, to attract an audience it inflames negative views about political opponents and makes exaggerated claims about the political stakes involved. Second, to capture and hold its audience, it makes it a priority to de-legitimate other sources of information.Footnote ³⁴ If a party’s voters come to rely on media outlets with incentives to polarize, and increasingly dismiss alternative sources of information, polarization is likely to become more intense and durable.

This is a necessarily truncated description of just some of the ways in which ongoing processes of nationalization and polarization have transformed critical meso-institutions. Even as formal institutional arrangements remain largely unchanged, these transformations – and the effects they in turn help generate, such as increasing tribalism and affective polarization among voters – may fundamentally alter the way discrete elements of the American polity fit together. In many cases, these developments did not just weaken the traditional generators of Madisonian pluralism; they transformed them into generators of intensified polarization. Interest groups and issues do not crosscut; they stack, one on top of the other, along partisan lines. When new issues arise, party politicians, existing groups, and politically aligned (and increasingly national) media, have incentives to push them into existing lines of partisan cleavage.Footnote ³⁵ Reflecting the growing forces of nationalization at work in our polity, geography no longer encourages pluralism, as it often did even during what are typically characterized as highly partisan eras. If state party competition focuses on intrastate dynamics, it will tend to be multidimensional, distinctive across states, and a source of moderation and plausible bipartisanship at the national level.Footnote ³⁶ However, where media and interest groups are nationalized, the role of geography may reverse. Nationalization puts the focus of state politics on the main national dimension, which means that even modest geographically based partisan inequalities may intensify over time.Footnote ³⁷ These conditions create incentives for local parties to elevate polarizing issues when they feel that highlighting the national partisan divide gives them an edge. Rather than serving as a brake, the strong role of territorially grounded representation in the American system may come to act as an engine of polarization.

Meso-institutions – social arrangements that are not formal (constitutional) rules – play a crucial and often underappreciated role in mediating interactions among American citizens, among political elites, and between elites and ordinary citizens. In earlier periods of polarization, these meso-institutions operated as countervailing mechanisms that (often quickly) dampened the intensity and breadth of partisan warfare. Partisan pushes away from centrist or consensus positions triggered a reaction. Crucially, these reactions did not simply depend – as they do in many traditional (Downsian) models of party competition – on the median voter’s political moderation and the responsiveness of officials to that voter. Downs postulated that electoral competition between parties would force parties to the middle. Yet many of the mechanisms limiting stark polarization, working mainly through the meso-institutional features described previously, operated primarily within parties rather than between them. American parties have been pluralistic and resistant to central direction, reflecting the competing concerns of interest groups, geographically diverse state parties, locally embedded media, and the distinct institutionally derived interests of politicians situated in different positions within our fragmented system of political authority.Footnote ³⁸

If polarization helps transform these intermediary institutions and their associated incentives, however, these self-correcting processes may cease to operate. When interest groups have strongly committed to a party and regard the stakes of party defeat as very high, they may find it prohibitively costly to push back against unwanted initiatives. State parties, operating in an increasingly nationalized system of incentives, may cease to produce the political diversity that would generate intraparty backlash. The same would be true for highly partisan media. In a transformed polity, all of these forces, which might in the past have generated dissent and signaled to voters that a party had moved to the extreme, may falter.

Checks and Balances in an Age of Intense Polarization

The changes in meso-level institutions described here have critical implications for the Madisonian system famously described by Neustadt as one of “separated institutions sharing powers.” We wish to focus on one particular implication, because it has such important ramifications for democratic stability and other key aspects of governance: the new political configuration changes the incentives of individual members of Congress in ways that make it considerably less likely that they will act in a manner that provides an effective check on executive power.

This is most obvious when there is unified party control of Congress and the White House. Shared partisanship has always encouraged members of Congress to be more receptive to presidential power claims and less likely to fight back when the president steps beyond prior understandings of the president’s role. Recent studies have shown, for example, that investigative oversight of the president by the House of Representatives was systematically lower under unified party control than divided control throughout the twentieth century. The impact of unified government on House oversight was higher in periods of high polarization than when polarization has been more muted, suggesting that when policy alignment between the president and the congressional majority is tighter, the incentives to investigate decline.Footnote ³⁹

Nonetheless, serious oversight was by no means absent in earlier periods of unified government. Indeed, the volume of Senate investigative activism was far less tied to divided versus unified control throughout the twentieth century, even under conditions of high polarization.Footnote ⁴⁰ The structure of meso-level institutions afforded substantial space for the president’s co-partisans to take on the White House in earlier eras. In particular, the relative autonomy of state parties meant that members’ career paths were far less dependent on pleasing the national party and its constituencies than is currently the case.

Perhaps the clearest example of this dynamic occurred during the New Deal and World War II. When southern Democrats became alarmed that the Roosevelt administration’s embrace of organized labor posed a threat to Jim Crow, southern members of Congress led aggressive investigations. Their oversight was designed not just to target particular Roosevelt policies, but to weaken an interest group that was a key pillar of the electoral base for both the president and their northern co-partisans. Noteworthy cases targeting the Roosevelt administration and its allies include Martin Dies’ (D-TX) investigation of Un-American Activities, Howard Smith’s (D-VA) onslaught against the National Labor Relations Board (and, a few years later, against the Office of Price Administration), and Eugene Cox’s (D-GA) investigation of the Federal Communications Commission.Footnote ⁴¹ For southern Democrats, the benefits of challenging a co-partisan president were substantial, while the costs were low. Those who led these investigations faced little risk of electoral repercussions for taking on the Democratic administration. Their own re-election was not contingent on either the national party’s standing or on the perception of national party leaders that they were “team players.” Roosevelt’s failed 1938 purge brought home the critical point: in a decentralized party system, winning reelection depended on appealing to locally rooted constituencies, regardless of whether this pleased either the president or other national party constituencies.

This relative autonomy of state parties was linked to another core aspect of meso-level institutions: the structure of interest group–party relations. The interest group coalition that backed Democrats in the north was fundamentally different from the constellation of interests critical in the south – indeed, in key respects the interest groups backing these party factions were fundamentally at odds.Footnote ⁴² Rather than relying on a nationally based network of activists and donors, Democrats in different regions were dependent on different groups. Some of these interests – such as business – were associated with different parties in different regions. For example, where business groups in much of the north gave mostly to Republicans, many businesses in the south and in New York City (the latter often led by Jewish entrepreneurs who were tied to the Democrats for ethno-cultural reasons) gave heavily to Democrats (Webber 2000). Instead of confronting an interest group universe that was nationally organized and often closely aligned with one party or the other, as is the case today, politicians of the same party often relied upon different types of groups depending on their local political economy and demographics. This again freed individual members to take on the president and his allied groups: the coalition of groups backing a southern Democrat in the 1940s did not view its interests as inextricably tied to the national-level party’s success.

A further crucial difference was the absence of a nationalized partisan media. Democrats in Congress could count on very different press coverage for either supporting or challenging national Democratic policies and groups depending on whether they were in the north or the south. Today’s national and partisan media supplies a key mechanism for enforcing cross-branch discipline, but the more decentralized press landscape in this earlier period operated very differently.

One might object that the New Deal era was an aberration, but other periods show some of the same dynamics, even if less dramatically. The Republican majorities of the 1920s repeatedly wrestled with regionally based party factions of farm and progressive members who dissented from key party positions and were willing to take coordinated actions that undermined the standing of the GOP administration (Bloch Rubin 2017). Most notably, progressive Republicans worked closely with Democrats in the early 1920s on the series of investigations that led to the disclosure of the Teapot Dome scandal and that ultimately forced the resignation of the attorney general. Unified Republican control did not prove a serious obstacle to major investigative oversight that seriously damaged the Republican administration’s standing.

Again, the space to criticize or challenge the president of one’s own party depended on meso-institutions working in a way that allowed members to see their own fortunes as not too dependent on their national party’s standing and success. For progressive Republicans, their nomination to office depended on appealing to voters who did not share the conservatism of national Republican leaders. They worked within a regionally based interest group landscape that was not a simple mirror of national-level Republican groups. They also could rely upon more localized press outlets that shared their skepticism of the national party’s positions and approach.

One indicator of the extent to which progressive Republicans saw their interests as partially independent of the national party was their willingness to cooperate with Democrats to scrutinize the “excessive” campaign spending of a handful of Republican Senate candidates. These actions actually resulted in the Republican Senate’s failure to seat incoming Republican members William Vare of Pennsylvania and Frank Smith of Illinois in 1927.Footnote ⁴³ The crucial point is that progressive Republicans of this era viewed their main constituency as fundamentally rooted in their home states. They believed that wooing those constituents was consistent with (and at times required) taking on their own national party.

Earlier periods of progressive activism within the GOP featured similar dynamics: the Ballinger-Pinchot investigation during the Taft administration – in which dissident Republicans joined with Democrats to attack the administration’s handling of public lands – is another example of the recurrent tendency for party factions to capitalize on their relatively independent electoral constituencies to take on a president of their own party.

Stepping back, these dynamics speak to a central theme in David Mayhew’s (2000) incisive account of the durability and flexibility of America’s Madisonian system. Repeatedly, members of Congress have engaged in significant actions in the public sphere that challenge or undermine the president. Mayhew’s systematic coding suggests that while clusters of opposition to the president may have been somewhat more likely under divided government, they have also been a recurrent feature of unified government. Mayhew argues that these oppositions have played a central role in checking presidential aggrandizement, alerting the public when the system of separated institutions sharing powers is under threat, and providing opportunities for the public to weigh in on major policy questions dividing the branches.

Today, the incentives facing members of Congress are far less conducive to this role. Consider a Republican member of Congress deciding how to respond to President Donald Trump. Regardless of one’s home state, the fear is the same: undermining the president carries serious political risks, particularly in a party primary. This fear reflects the changes in meso-level institutions. In place of the relatively autonomous state parties of earlier decades, Republican members are embedded in a national party network of activists and donors who share a commitment to much the same conservative policies, and to the established partisan alliances that support them. Given the sharp divide between the two parties, they are deeply hostile to any actions that would benefit the Democratic opposition. They also confront an interest group universe that is more national in scope and more clearly tied to party. There is no major alternative source of support out there if a member alienates the groups with strong ties to their party. Because today these groups identify their own success much more closely with that of the party, they have a stronger incentive to penalize failures to be a good team player. Perhaps most importantly, the nationalized and partisan media – Fox News, talk radio, and online – mean that a member risks coordinated, concerted criticism for taking on the president.

All of this adds up to a strong incentive for members to stick with a president of their own party. Indeed, the current institutional configuration makes remaining loyal to one’s party by far the easiest choice. Denying everything and attacking the other side is a safe strategy, particularly when one can count on partisan media to amplify this message and discount alternative narratives. The net result looks a lot like tribalism, but for those valuing political survival it can be firmly grounded in a cold calculation of personal interest rather than emotion or identity.

This tribalism has different – yet perhaps equally troubling – implications for the resilience of Madisonian separation of powers under divided and unified government. As noted, the primary concern under unified government is that the majority party in Congress will block serious efforts to investigate or roll back presidential excesses. Under divided government, one surely can expect plentiful congressional efforts to investigate and fight back against the president – indeed, intense polarization sharply increases the incentives of the other party to go after the White House. But absent any significant buy-in from the president’s party, the risk is that these congressional actions will be far less effective.

We conventionally classify government as divided if the president’s party does not control at least one chamber of Congress; but it may make a big difference to Congress’s ability to fight back on policy if different parties control the House and Senate.Footnote ⁴⁴ Losing control of a single chamber can create problems for the president’s party. In the process they lose considerable agenda control, greatly increasing the prospects for potentially damaging investigations. Yet retaining control of a single chamber limits the capacity of Congress to take robust action.Footnote ⁴⁵ This distinction likely existed in earlier eras, but it is exacerbated when intense polarization leads the president’s co-partisans to view defecting from the White House as prohibitively costly.

When it comes to direct policy-making, polarization under divided government makes it harder for Congress to fight back effectively against presidential unilateral actions. President Trump’s decision to shift funds to build the border wall is a telling example. The president’s declaration of a national emergency was widely understood to be a breach of prior use of emergency declaration powers, and was directly counter to Congress’s decision with respect to its core power of the purse. Yet even in the presence of expedited procedures that allowed a simple majority in each chamber to pass a resolution overturning the president’s action, Trump’s veto power, backed by a clear majority of House and Senate Republicans, proved sufficient to block a reversal. Congressional efforts to fight back on policy are also hampered when control of the two chambers is divided. The need to win Senate Republicans’ agreement has undermined House Democrats’ efforts to use subsequent spending bills to block further reprogramming of funds. This stands in sharp contrast to the early 1970s, when Nixon threatened congressional control of the purse with his aggressive use of impoundments. Then, a near-unanimous Congress adopted the Congressional Budget and Impoundment Control Act of 1974, which imposed major restrictions on the president’s ability to control spending.Footnote ⁴⁶

Although this warrants more discussion than we can offer here, it is important to emphasize that the character of modern polarization we have described has other worrisome effects on the complex interplay within a system of fragmented political authority. Even if Congress is able to limit or neutralize presidential unilateral actions, continuous interbranch battles under divided control may give rise to policy immobilism and a sense of deep political dysfunction that contributes to long-term democratic erosion. The American political system has generally required the construction of broad, cross-party coalitions to enact major legislative change. Intense polarization sharply diminishes the prospects for such coalitions. It is not just that the parties are further apart, although it is obviously harder to compromise when the two parties want to move in opposite directions. Irrespective of policy goals, the political competition between the parties is increasingly zero-sum, making it difficult or impossible to locate agreements that both sides will see as wins. And the challenge is worsened when affective polarization, egged on by partisan media and extreme groups, bolsters the view that compromise constitutes betrayal. When such coalitions are much harder to construct, policy challenges may fester, heightening frustration with existing institutions. A sense of democratic dysfunction is particularly dangerous in a context of tribalism where an aspiring demagogue can count on party loyalty to provide a solid base of support for efforts to sweep aside traditional institutional constraints on their actions.

Increasing party loyalty doesn’t just make it more difficult for Congress to take action. Solidarity within the president’s party makes it much harder to portray investigative efforts as transcending partisan conflict. As a result, investigations may have less impact on public opinion (which in turn makes it easier for co-partisans to stay loyal to the president). Changes in the media environment further weaken the potential impact of Congressional action. The decline of “neutral arbiters” in the press means that the main signals that the public will receive inevitably come from partisan elites on either side. If Republicans can be counted on to stick with a president of their party and if Democrats can be assumed to have strong political incentives to oppose the president, many voters will be tempted to view what happens in congressional hearing rooms as little more than partisan position-taking. Mayhew’s concept of members taking significant actions in a “public sphere” presupposes sufficient member independence so that citizens may well change their minds in response to what they see members doing. But if the president’s party is unified in dismissing serious investigations as mere partisan witch-hunts, voters may be resistant to updating their views in response. In sufficiently extreme cases, the sheer weight of evidence may move enough voters and elites for investigations to have a meaningful impact. But the hurdle for doing so is arguably much higher than it had been in the past. Even as most Republicans stuck with President Nixon throughout the Watergate scandal, consequential fissures emerged among Republicans. These fissures, in turn, likely reinforced the public’s sense that the scandal was not simply “politics as usual.”

We have described these incentives in general but the focus here on Republicans is not simply illustrative. These dynamics are especially strong for Republicans due to differences in the meso-institutional environment facing the two parties’ members – indeed one of the important analytical advantages of our approach is its utility for exploring and explaining differences between the two party coalitions in contexts where each operates within identical formal institutions. The polarizing role of contemporary federalism that we have noted operates more weakly for Democrats, given the unfavorable geographic distribution of the party’s voters. The growing concentration of Democratic voters in urban areas is, within the American electoral framework, politically inefficient (Rodden 2019). As a result, a Democratic victory in Congress requires winning red-leaning districts and states, creating an incentive to moderate and/or tolerate heterogeneity within the party. Republicans, by contrast, receive an electoral bonus from this political geography, facilitating a move to the right and diminishing the need to tolerate intraparty dissent. Speaker Pelosi’s delicate balancing act in approaching competing views of impeachment through much of 2019 was a telling example of Democratic leaders’ perception that protecting their vulnerable members has to be a top consideration if the party is to retain its majority.

At least as important, the media environment for the two parties is fundamentally different. As Grossmann and Hopkins show, the conservative media ecosystem, which developed partly in response to perceived mainstream media bias, created news outlets that were explicitly tied to conservative organizations and causes.Footnote ⁴⁷ From the outset, conservative media placed considerable emphasis on the task of discrediting alternative sources of information. Grossmann and Hopkins note, “the strategy was self-reinforcing, as right-leaning citizens came to rely more on conservative media and become less trusting of other news sources.”Footnote ⁴⁸ The media ecosystem on the right is far more isolated from the informational mainstream than that of the left.Footnote ⁴⁹ Messages from conservative media sources have worked to activate the existing symbolic predispositions of their audience, insulated viewers from countervailing forms of influence, and have increased vulnerability to conspiracy thinking.Footnote ⁵⁰ Recent evidence suggests that Fox News – itself just one part of the conservative media ecosystem – has in fact pushed viewers’ opinions further to the right.Footnote ⁵¹ Fox now finds itself challenged from outlets that are more extreme, such as One America News and Newsmax, reinforcing the message that on the conservative side, there is a strong incentive not to be outbid from the right.

Although empirical research on this topic is less developed, these differences seem likely to exist on the interest group side as well. GOP networks seem to involve fewer, but very powerful groups – especially the Christian right and organized economic elites – with ambitious policy agendas that drive the entire party rightward. The Democratic coalition, by contrast, is made up of a wider range of interests, each of them demanding a say but none of them (especially given the decline of organized labor) large enough to dictate priorities. Furthermore, the shift of political resources to the wealthy and corporations amid rising inequality has different implications for the two parties.Footnote ⁵² For a left-leaning party, growing inequality in economic and political power exerts a moderating influence at least on many economic issues, encouraging the party to resist pulls to the left. For the GOP, however, a growing concentration of economic power, mobilized by organizations like the Koch network and the Chamber of Commerce, has pushed the party to the right (Hertel-Fernandez and Skocpol 2016).Footnote ⁵³

Republicans also face a distinct and formidable challenge: powerful demographic trends that are unfavorable to its existing coalition. In the past, parties facing such trends would have had both strong incentives and considerable capacity to adapt. Indeed, a striking feature of American political history is the impressive ability of parties to shift their positions on issues and incorporate appeals to rising demographic groups, even when doing so required weakening ties to groups in decline.Footnote ⁵⁴ Some Republican moderates have urged the party to act similarly, most famously with the RNC’s “autopsy report” after Mitt Romney lost in 2012, but the shifts in the meso-environment we have described have made this kind of adaptation considerably more difficult. As the party and aligned interest groups become more tightly intertwined, organized resistance to efforts to moderate and to incorporate new groups is likely to grow.Footnote ⁵⁵ Groups will often be far less willing than politicians to throw prized policies overboard. The emergence of partisan media, working with a profit model based on stoking identity and outrage, only worsens the problem. Adaptation may be labeled betrayal, and the capacity of partisan media to punish undesired behavior has grown. Rather than reaching out to ascendant groups and incorporating new issues, a party facing demographic threats under current conditions may choose to intensify efforts to mobilize its existing coalition. Even more troubling, it may see advantages in restricting access of these ascendant groups to the public sphere. The associated risk for democratic backsliding is evident.

Conclusion: Polarization in a Madisonian Framework

Intensifying polarization in the context of the transformed meso-institutional environment that we have described poses a genuine challenge to the robustness of Madisonian separation of powers and checks and balances. This is by no means the first threat to American democratic institutions. Political scientists and historians have long made it clear that these institutions were woefully flawed when it comes to critical dimensions of inclusion and responsiveness for much of American history. Our argument is that the particular threats and problems we face today are distinctive – and that they jeopardize core assumptions about the self-correcting tendencies of a system in which “ambition is made to counteract ambition.”

We have emphasized some of the ways in which the current configuration of meso-institutions, formal institutions and party competition can erode the quality of governance, undercutting the capacity to reach a consensus on and address major problems, and diminishing the prospects for effective oversight. In this conclusion we focus, however, on how our developmental perspective allows us to situate the evolution of the American polity within the ongoing comparative discussion of democratic backsliding. We have already noted the efforts of Juan Linz to draw out the ways in which American institutions generated weak parties, which limited the dangers he saw lurking in presidential systems. In the contemporary period of intense polarization, however, American parties look less distinctive. Most important, this new political configuration seems far less effective at generating crosscutting pressures and a multiplicity of fluidly aligned interests. Increasingly, incentives for party loyalty appear to trump incentives associated with the particular institutional location of a political representative within our institutionally complex constitutional order.

Yet the challenge this new configuration creates doesn’t simply involve the potential conflict between two branches, each with well-grounded claims to legitimacy, stressed in Linz’s account. While this remains a plausible scenario, the rise of stronger incentives for party loyalty also suggests new vulnerabilities in a system that relies heavily on each branch to police the others.

The strengthening pull of party loyalty across the separation of powers system has been on vivid display in the final year of Donald Trump’s presidency. Republicans’ near-perfect unity in defending President Trump during the impeachment battle in early 2020 begged the question of whether there was any possible evidence of wrongdoing that would lead a substantial number of Republicans to emulate the conduct of their fellow-partisans during the Nixon years. While Nixon-era Republicans showed a strong inclination to side with the president, in the end a third of Republicans on House Judiciary backed impeachment, and pivotal senators eventually made it clear to the president that they would vote to convict. It is hard to imagine any “smoking-gun” evidence that would have led more than a very small handful of Republicans to take such action in 2020.

The willingness of elected Republicans to tolerate or openly support President Trump’s baseless attack on the legitimacy of the 2020 election was equally revealing. When 126 House Republicans signed an amicus brief adopting the unprecedented position that the electoral votes of four states should be thrown out in order to overturn President Trump’s defeat, many speculated on whether these members truly believed their own argument or were simply position-taking to curry favor with Trump. But this misses the essential point. A clear majority of House Republicans – and a considerably higher proportion of those who were not retiring – adopted a position that would have been politically inconceivable a few decades ago: that millions of votes ought to be thrown out in order to secure their candidates’ victory. Regardless of whether these members believed their own argument or expected to have any concrete impact on the Court, their willingness to sign the brief was a clear indicator that loyalty to the president outweighed any commitment to long-standing democratic rules of the game.

Our analysis supports the view of Roberts and others that these new circumstances have made the parties, and especially the GOP, vulnerable to what comparativists call “bandwagoning.”Footnote ⁵⁶ Bandwagoning is a process in which disparate elites within a coalition face growing incentives to go along with extremist or antidemocratic practices.Footnote ⁵⁷ A developmental perspective suggests that the prospects for bandwagoning are much greater in today’s GOP than they might have been a few decades ago. What Roberts calls the “movementization” of the GOP creates new incentives for political elites to stick with their team on matters – including challenges to established norms of restraint and tolerance, the rule of law, and the integrity and autonomy of core democratic institutions – where previously they might have chosen to dissent.Footnote ⁵⁸ In this chapter, we have focused on Congress, but we should note that while some of the analysis would require modification, many elements would also apply to the courts. Partisan loyalty and fealty to party-aligned groups and causes are increasingly important parts of the process through which judges are selected.

The American system of checks and balances, with its unusual dispersal of political authority, has long generated formidable barriers against democratic backsliding.Footnote ⁵⁹ Yet many of the stabilizing forces that traditionally were linked to these institutions seem much weaker today. In fact, in some cases, these arrangements now introduce new polarizing elements. For instance, the Madisonian system of territorial representation may create a powerful incentive for bandwagoning that is absent in systems lacking that feature. The stacking of cleavages in our polarized system has helped to deepen the territorial divide between the electorates of the two parties. Increasingly, elected officials find themselves facing local electorates dominated by a single party, further undercutting the effectiveness of traditional Downsian mechanisms for limiting extremism.

Most important, the United States is unusual in its heavy reliance on checks and balances to insure democratic stability. In many democracies, electoral arrangements that encourage multiparty systems in which no single party is likely to dominate play a central role. Our two-party system has been grounded in a structural decentralization of political authority. Yet the emergence of hyper-partisanship means that the check on authoritarian developments in the presidency that the Madisonian system relies on most, Congress, may not work. Instead, GOP members of Congress in particular face multiple incentives to bandwagon rather than resist. Among those incentives are the intense preferences of the party’s interest groups, the heavily “red” and negatively partisan electoral bases of these politicians, and the likelihood that influential partisan media will exact a very high price for defection. Given these realities, it is perhaps unsurprising when even the most extreme and disquieting behavior in a Republican White House fails to shake the solidarity of Republican members of Congress. In short, the developmental perspective we offer raises a disturbing prospect: Under conditions of hyperpolarization, with the associated shifts in meso-institutional arrangements and the growth of tribalism, the Madisonian institutions of the United States may make it more vulnerable to democratic backsliding than many other wealthy democracies would be.