Metrics, methods, and political implications

Assessing gerrymandering remains a complex task, partly because of the absence of universally accepted standards – either statistical or legal – for determining whether a district is non-compact or manipulated. As Niemi et al. (Reference Niemi, Grofman, Carlucci and Hofeller1990) highlight, there is no widely agreed-upon benchmark for what constitutes an acceptable level of district shape or irregularity, and the legal literature on districting often relies on subjective assessments. Beyond geometric measures, many scholars and policymakers have historically relied on compactness as an indicator of district fairness, assuming that regular, simple shapes are less manipulable. However, extensive research indicates that compactness alone offers limited insight. Altman (Reference Altman1998) demonstrates that emphasizing geometric regularity often fails to detect or prevent strategic gerrymandering, especially since natural geographic clustering – such as densely populated urban areas – can produce districts that are both compact and heavily skewed in partisan terms. In fact, Chen and Rodden (Reference Chen and Rodden2013) show that the geographic concentration of Democratic voters leads to representational biases even when districts are drawn to uphold basic redistricting principles like compactness. Young (Reference Young1988) emphasizes that interpretations of compactness vary considerably across jurisdictions, resulting in inconsistent and often unreliable assessments of district fairness.

Recognizing these limitations, scholars advocate for a broader, more comprehensive evaluation of districting plans. Niemi et al. (Reference Niemi, Grofman, Carlucci and Hofeller1990) argue that assessing complete districting plans – rather than individual districts based solely on shape – is critical for understanding the true extent of partisan bias. By evaluating the overall configuration and considering multiple criteria simultaneously, researchers can better capture the multifaceted nature of gerrymandering. Building on this approach, Ansolabehere and Palmer (Reference Ansolabehere and Palmer2016) analyze historical data, showing that while compactness has fluctuated, it consistently falls short in detecting partisan manipulation, which often manifests in subtle configurations not captured by geometry alone.

In recent years, the development of outcome-based metrics has marked a significant advance in the field. Quantifiable measures of gerrymandering have long been used by political scientists since King and Browning (Reference King and Browning1987) and Gelman and King (Reference Gelman and King1994) developed measures of partisan symmetry – bias and responsiveness – advancing early work by Tufte (Reference Tufte1973) and Taagepera (Reference Taagepera1973) attempting to characterize the nature of the votes–seats relationship. More recently, Stephanopoulos and McGhee (Reference Stephanopoulos and McGhee2015) introduced the efficiency gap, which assesses gerrymandering based on the extent to which “wasted” votes favor one party over another – where wasted votes are those that exceed what is necessary to win a district. Similarly, McDonald and Best (Reference McDonald and Best2015) offered a simple and transparent metric to assess the distribution of votes across districts using the mean–median difference. And Warrington (Reference Warrington2018) presented an alternative method for evaluating vote distributions using the declination – which captures asymmetries in the vote distribution on either side of the 50% threshold required for victory. Altogether, these metrics shift focus from district shape to actual electoral outcomes, providing a more direct indicator of gerrymandering. Outcome-based measures like partisan symmetry, efficiency gap, mean–median, declination, and others are now central to empirical work, offering policymakers and courts tools for evaluating fairness with greater precision.

Furthermore, the advent of advanced computational methods has revolutionized the empirical analysis of gerrymandering. Modern algorithms can generate large ensembles of districting plans that meet basic legal and procedural standards – such as contiguity, population equality, and compactness – but lack intentional partisan design. These plans serve as neutral benchmarks or counterfactuals, allowing researchers to compare actual district maps against a vast pool of plausible, nonpartisan alternatives. For example, scholars like McCarty, Poole, and Rosenthal (Reference McCarty, Poole and Rosenthal2009), Chen and Rodden (Reference Chen and Rodden2013), Chen and Cottrell (Reference Chen and Cottrell2016), Magleby and Mosesson (Reference Magleby and Mosesson2018), Herschlag et al. (Reference Herschlag, Kang, Luo, Bangia, Schutzman, Graves and Mattingly2018), Cottrell (Reference Cottrell2019), Deford, Duchin, and Solomon (Reference DeFord, Duchin and Solomon2021), Kenny et al. (Reference Kenny, McCartan, Simko, Garcia, Kuriwaki and Imai2023) and others use computer algorithms to generate an ensemble of alternative plans per state. These plans are constructed to adhere to procedural criteria but exclude partisan manipulation, thus serving as a baseline for detecting gerrymandering. By comparing actual districts to these simulated ensembles, researchers can quantify how much of the observed partisan bias or seat safety can be attributed to strategic redistricting versus natural voter geography.

While many of these simulation studies focus on gerrymandering within a single state, a few have examined its effects on representation broadly across all U.S. House seats. These broader studies yield a range of insights, but perhaps the most striking is their consistent conclusion that gerrymandering has had only a modest effect on political representation in Congress. For example, McCarty, Poole, and Rosenthal (Reference McCarty, Poole and Rosenthal2009) find that gerrymandering contributes only marginally to polarization; Chen and Cottrell (Reference Chen and Cottrell2016) show that while both parties gain seats from gerrymandering, these advantages largely offset one another; and Cottrell (Reference Cottrell2019) demonstrates that although gerrymandering substantially reduces the number of competitive districts, its effect on the average incumbent’s likelihood of winning is relatively small compared to the natural advantages caused by the geographic patterns of polarization. More recently, Kenny et al. (Reference Kenny, McCartan, Simko, Garcia, Kuriwaki and Imai2023) leveraged advanced simulation techniques to analyze the effects of the 2020 redistricting cycle and reached similar conclusions – gerrymandering has a modest effect on reducing overall levels of competitiveness, but its aggregate partisan effects largely cancel out.

Importantly, these methods provide policymakers, courts, and researchers with transparent, quantitative assessments. Objective benchmarks created through simulation enable more precise evaluations of partisan bias, informing legal rulings and reform proposals. As computational capabilities and data granularity improve – with precinct-level voting data and faster algorithms – these methods will increasingly shape empirical debates and potential legislative reforms. In recent years, the Supreme Court has acknowledged measures like the “efficiency gap” as potentially useful tools for evaluating redistricting plans. However, in cases such as Rucho v. Common Cause (2019), the Court ultimately declined to adopt such metrics as judicially manageable standards, concluding that claims of partisan gerrymandering present political questions beyond the reach of federal courts.

Looking forward, future research can deepen understanding by integrating these simulation tools with investigation into how specific legal and institutional contexts influence the design and outcomes of redistricting. For example, examining how different states implement districting algorithms or how courts evaluate gerrymandering using simulation benchmarks can reveal the practical limitations and opportunities of these methods. Additionally, expanding their use to analyze the impacts on actual electoral competitiveness – beyond seat counts or partisan bias – can enhance our understanding of how redistricting shapes voter choices and representation across diverse political environments.

Overall, the development and application of simulation techniques represent a major advancement in empirical political science research on gerrymandering. By providing a rigorous, data-driven basis for comparing actual maps to neutral benchmarks, they help clarify the extent and effects of partisan manipulation. As computational power and data accessibility continue to improve, these methods will become even more central to normative debates, legal challenges, and policy reforms aimed at achieving electoral fairness and competitive integrity.

Despite recent innovations, political and demographic shifts often produce unexpected competitive dynamics, as evidenced by historical analyses like Carson, Engstrom, and Roberts (Reference Carson, Engstrom and Roberts2006), who draw parallels with past practices of candidate entry and incumbency protection. Makse (Reference Makse2014) highlights how state legislatures increasingly push the boundaries of constitutional limits – such as redrawing boundaries more frequently – to secure partisan advantages, reflecting ongoing tensions between legal constraints and strategic ambitions (Engstrom Reference Engstrom2013; Levitt and McDonald Reference Levitt and McDonald2007). Carson, Engstrom, and Roberts (Reference Carson, Engstrom and Roberts2006) also provide insights into how redistricting cycles influence candidate entry, showing that early redistricting can foster greater competition and challenge incumbents, a pattern consistent with Seabrook’s (Reference Seabrook2017) findings on the fleeting nature of partisan gains. As Hetherington, Larson, and Globetti (Reference Hetherington, Larson and Globetti2003) note, timing plays a crucial role; districts drawn early in the cycle are more susceptible to shifts in electoral context, and Goedert (Reference Goedert2017) illustrates how partisan advantages carved into districts can erode over time in response to national trends, highlighting the inherent instability of long-term partisan benefits.

Furthermore, the legal landscape governing redistricting remains contested. Levitt and McDonald (Reference Levitt and McDonald2007) discuss state constitutional provisions and how states circumvent them to allow mid-cycle redistricting, often to pursue immediate partisan gains. Engstrom (Reference Engstrom2013) documents how such practices have historically been used not only to respond to demographic changes but also to secure partisan advantages when control of legislatures shifts. Makse (Reference Makse2014) emphasizes how strategic legal navigation requires resilience and adaptability from political actors, underscoring redistricting as a dynamic and vital component of electoral strategy. This ongoing legal and strategic evolution underscores the limitations of traditional measures – such as geometric compactness – in capturing manipulation.

The variable impact of different redistricting methods

The question of whether partisan redistricting reduces electoral competition has long been debated. Some researchers, like Ferejohn (Reference Ferejohn1977), argue that gerrymandering can significantly distort competition, creating safe seats that diminish electoral volatility. However, McDonald (Reference McDonald2006) points out that these findings depend heavily on the measurement approaches used – highlighting methodological variability as a key factor shaping conclusions. In exploring historical patterns, Engstrom (Reference Engstrom2006) investigates 19th-century redistricting plans, illustrating that tactics of the past can inform current understanding of strategic behaviors and their influence on competitiveness. Additionally, Gelman and King (Reference Gelman and King1994) and Yoshinaka and Murphy (Reference Yoshinaka and Murphy2011) offer a counter view, suggesting that partisan mapping sometimes enhances electoral processes, particularly where it facilitates clearer ideological choices and voter alignment, challenging the notion that all partisan gerrymandering undermines fairness.

While electoral competition is often seen as essential for a healthy democracy, some scholars contest this view by emphasizing representation over competition. Buchler (Reference Buchler2005) argues that highly competitive elections do not necessarily produce outcomes that best reflect the electorate’s preferences, raising questions about whether competition should be a primary goal. Similarly, Brunell (Reference Brunell2008) suggests that overly contest-driven systems might erode voter satisfaction, fostering instability, and disengagement rather than genuine legitimacy. These perspectives challenge the conventional emphasis on competition and suggest we should consider the quality of representation and voter connection as equally, if not more, important for democratic health.

Beyond the debate over fairness, scholars also examine broader trends influencing electoral dynamics. Abramowitz, Alexander, and Gunning (Reference Abramowitz, Alexander and Gunning2006) highlight that the decline in competition is increasingly tied to political polarization and incumbency advantage, which reinforce existing power structures regardless of redistricting practices. Brunell (Reference Brunell2008) extends this argument, pointing out that voter dissatisfaction may stem from a complex interaction of demographic shifts and political stratification, rather than redistricting alone. Engstrom (Reference Engstrom2006) reinforces that when one party controls redistricting, it can tilt electoral outcomes in its favor, though such advantages tend to be temporary as shifting political climates and demographic changes counteract initial gains. And McDonald (Reference McDonald2004) emphasizes that those same advantages can be attenuated by the type of redistricting institution, which varies across states and across state and federal redistricting. These findings underscore the debate’s complexity: various factors – legal, strategic, demographic, and institutional – intersect to shape electoral competitiveness over time.

Despite the diverse viewpoints on redistricting’s effects, its potential role in enhancing democratic responsiveness should not be overlooked. Gelman and King (Reference Gelman and King1994) argue that, when implemented with careful consideration, redistricting can increase representatives’ accountability and responsiveness to their constituents, thereby strengthening overall democratic engagement. Although Ferejohn (Reference Ferejohn1977) emphasizes a long-term decline in electoral competition, other scholarship (see, e.g., Cain Reference Cain2012) suggests that redistricting can also serve as a tool for democratic refinement – providing opportunities to improve representation and accountability. This multifaceted discourse invites ongoing investigation into how redistricting, when properly managed, can support both fair and effective governance, moving beyond the narrow focus on political advantage to broader democratic outcomes.

Building on this discussion of redistricting’s potential to foster democratic responsiveness, independent commissions are frequently proposed as a solution to depoliticize redistricting and promote electoral fairness. Since these bodies are designed to operate with greater objectivity, proponents argue they can produce more competitive districts by applying consistent criteria and reducing partisan influence (Carson, Crespin, and Williamson Reference Carson, H. Crespin and Williamson2014; Lindgren and Southwell Reference Lindgren and Southwell2013). Empirical studies support this optimism: Cottrill (Reference Cottrill2012), Crespin and Edwards (Reference Crespin and Edwards2016), and Edwards et al. (Reference Edwards, Crespin, Williamson and Palmer2017) find that commission-led redistricting tends to yield more competitive environments, notably by reducing the number of unopposed incumbents and aligning districts more closely with principles such as compactness and community integrity.

Recent research, such as Nelson (Reference Nelson2023), provides robust quantitative support for these claims, showing that states using independent commissions are roughly 2.25 times more likely to produce competitive races and tend to decrease incumbent victory rates by about 52%. Chen and Cottrell (Reference Chen and Cottrell2016) and Cottrell (Reference Cottrell2019) find that the effect of gerrymandering is less pronounced in states with nonpartisan redistricting. And moreover, Williamson (Reference Williamson2019) and Williamson (Reference Williamson2024) add that nonpartisan plans generally foster higher candidate quality and long-term electoral competitiveness. However, Williamson (Reference Williamson2024) also emphasizes that the success of these reforms depends heavily on implementation quality, institutional independence, and the broader political environment.

Building on this, Hayes (Reference Hayes2024) provides evidence that the contrasting effects of redistricting institutions extend to the types of group representation they promote. His analysis shows that institutional design determines whether districts favor partisan, geographic, or racial/ethnic group representation, with independent commissions facilitating multiple forms of group inclusion depending on their specific criteria. This highlights that the impact of commissions is not uniform and depends on how they are structured and operate, reinforcing the complexity of evaluating their overall effectiveness.

While some studies highlight favorable effects, others draw more cautious conclusions. Masket, Winburn, and Wright (Reference Masket, Winburn and Wright2012) and Henderson, Hamel, and Goldzimer (Reference Henderson, Hamel and Goldzimer2018) challenge the assumption that independent commissions substantially alter overall competitiveness. These studies argue that, although commissions often introduce structural changes, their impact on reducing partisan bias might be limited in practice. Henderson, Hamel, and Goldzimer (Reference Henderson, Hamel and Goldzimer2018) further question whether commissions can fully resist embedded political interests – suggesting that partisan influence can persist even within ostensibly neutral bodies.

Supporting this cautious view, Lindgren and Southwell (Reference Lindgren and Southwell2013) observe that commission-led redistricting, while beneficial in many instances, is not a guaranteed solution. Their findings suggest that commissions can catalyze meaningful change by introducing alternative dynamics into electoral contests, but their effectiveness varies depending on design, legal context, and political landscape. This divergence underscores the complexity and nuanced nature of redistricting reform – highlighting that commissions are neither a panacea nor a failure, but institutions whose success depends on multiple conditions. However, more recent research suggests that the value of commissions may not lie in the outcomes they produce, but instead in the way they can confer greater legitimacy on the redistricting process. Williamson and Justwan (Reference Williamson and Justwan2025) find that knowing a commission drew maps (instead of a state legislature) increases perceived legitimacy and overall satisfaction with the outcomes – even if the two plans are identical.

Building on the discussion of independent commissions as an alternative to partisan redistricting, courts also play a significant role in shaping the redistricting landscape. Both institutions are often seen as mechanisms that can mitigate partisan manipulation and promote electoral competition, serving as counterbalances to self-interested legislative plans. However, as past scholarship reveals, the actual effects of judicial intervention are more nuanced. Courts may enforce standards aimed at fairness and competition, but their decisions are shaped by legal interpretation, political influences, and case-specific considerations that complicate their overall impact.

Courts are called upon to arbitrate disputes, enforce legal standards such as “one person, one vote” (Persily, Kousser, and Egan Reference Persily, Kousser and Egan2002), and review claims of partisan gerrymandering. Landmark cases like Gill v. Whitford (Hirsch Reference Hirsch2003) have set significant precedents with respect to redistricting, shaping modern understanding of what constitutes unconstitutional partisan manipulation and influencing subsequent districting practices. Scholars such as Cottrill and Peretti (Reference Cottrill and Peretti2013) suggest that judicial rulings can help enhance electoral competition by curbing overt partisan excesses, providing a check on abuses of power.

Despite these potential benefits, the relationship between judicial decisions and partisan influence is complex. The debate centers on whether courts act as neutral enforcers or whether their rulings reflect underlying political biases. Lloyd (Reference Lloyd1995) and McKenzie (Reference McKenzie2012) highlight that judges may sometimes allow political considerations to influence their rulings, whether intentionally or subconsciously. Recent research by Peterson (Reference Peterson2019) further complicates the picture, demonstrating that judges often produce district maps that are more competitive than those drawn by legislatures or commissions, but that these maps can still favor distinct partisan interests – effectively masking strategic calculation under a veneer of neutrality. This tension underscores the inherent challenge courts face in balancing normative standards of fairness with the realities of partisan politics.

Overall, the influence of courts in redistricting exemplifies the ongoing challenge of maintaining electoral integrity within a highly politicized environment. Judicial decisions can serve as valuable tools to promote fairer districts, but their effectiveness is ultimately shaped by the norms, legal standards, and political contexts within which courts operate. As scholars continue to examine these dynamics, it becomes clear that the judiciary plays a crucial role – sometimes mitigating partisan bias, but at other times reinforcing existing divides – highlighting the persistent tensions in efforts to achieve equitable representation.

Institutional design significantly influences redistricting outcomes, with practices like prison gerrymandering exemplifying how legal and procedural choices can distort fairness and representation. Counting incarcerated individuals at their prison locations, rather than their home districts, can skew demographics, resource allocation, and voting power. Wang and Devarajan (Reference Wang and Devarajan2019) report cases where prison populations in some districts exceed nonincarcerated residents, raising fairness concerns. Remster and Kramer (Reference Remster and Kramer2018) note this disproportionately impacts urban, non-white communities, while Drake (Reference Drake2011) and Skocpol (Reference Skocpol2017) argue it may violate “one person, one vote” principles by inflating certain populations’ influence.

Research highlights socioeconomic consequences, with Walker et al. (Reference Walker, Thorpe, Christensen and Anderson2016) pointing out that counting methods affect resource distribution, often favoring rural districts. Kelly (Reference Kelly2012) shows mapmakers exploit prison populations to create partisan advantages, benefiting rural, and Republican-leaning areas. Jacobson (Reference Jacobson2015) also suggests this redistribution benefits Republicans, who tend to be more dispersed in rural regions, contrasting with urban Democrats. Such counting practices can influence electoral outcomes and district compositions.

Recent reforms in California, Colorado, Maryland, New York, and Washington now count incarcerated individuals at their home addresses for redistricting. Williamson and King (Reference Williamson and King2022) find that New York’s policy shifts significantly impacted state elections between 2002 and 2020. Continued research is needed to assess long-term effects of these reforms on electoral fairness, representation, and political balance.

In conclusion, the evolving landscape of redistricting highlights numerous avenues for future political science research. Further investigation is needed to assess the long-term impacts of institutional reforms such as independent commissions and judicial oversight on electoral outcomes and representation. Additionally, examining the effects of practices like prison gerrymandering can yield insights into how procedural choices influence district demographics and resource allocation. Continued empirical analysis is essential to understand the conditions under which different redistricting approaches produce measurable changes in competitiveness and fairness.

How redistricting influences candidacy, victory, and voting behavior

Redistricting is a key factor in shaping electoral competition and political dynamics within the US. Its influence on polarization and incumbency has been the focus of extensive scholarly inquiry, revealing a complex interplay of factors that go beyond the act of drawing district boundaries. While public discourse often frames redistricting as a primary driver of increased polarization, seminal works by Theriault (Reference Theriault2008) and McCarty, Poole, and Rosenthal (Reference McCarty, Poole and Rosenthal2009) challenge this view, suggesting that broader socio-political and economic factors play a more significant role in driving polarization. They argue that while gerrymandering can amplify partisan leanings in specific districts, it is not the main or sole cause of systemic political divides. This perspective shifts the focus from district boundaries to wider influences when understanding polarization.

Supporting this view, DeVault (Reference DeVault2013) emphasizes that redistricting’s contribution to issue-specific polarization – such as in trade policy debates – is limited. Similarly, Ryan and Lyons (Reference Ryan and Lyons2014) argue that modifications to redistricting practices alone are insufficient to resolve deeply entrenched partisan divisions. However, contrasting findings from Grainger (Reference Grainger2010) and Brunell and Buchler (Reference Brunell and Buchler2009) highlight scenarios where redistricting, particularly when driven by legislative agendas, can exacerbate polarization – as exemplified in California’s distinctive political landscape. Carson et al. (Reference Carson, Crespin, Finocchiaro and Rohde2007) offer a nuanced perspective, acknowledging that while redistricting influences polarization, it interacts with a mosaic of other factors that collectively shape political behavior.

The relationship between redistricting and incumbency also has deep historical roots. Tufte (Reference Tufte1973) pointed out that strategic redistricting in the 1960s strengthened incumbent advantages, laying the groundwork for later research on how district boundary changes influence electoral stability. Studies by Ansolabehere, Snyder, and Stewart (Reference Ansolabehere, James M. and Charles Stewart2000), Desposato and Petrocik (Reference Desposato and Petrocik2003), and Hood and McKee (Reference Hood and McKee2010) suggest that redistricting can reduce incumbency advantages by reshuffling voter bases, making incumbents more vulnerable to demographic shifts and electoral pressures. These changes can prompt experienced politicians to reconsider their candidacies, creating opportunities for new contenders. At the same time, McGann et al. (Reference McGann, Smith, Latner and Keena2016) document several extreme partisan gerrymanders in the 2012 House elections – most notably in North Carolina – underscoring that well-designed partisan plans can be highly effective at converting votes into seats (as Texas’s 2004 mid-decade remap also illustrates).

Over time, Friedman and Holden (Reference Friedman and Holden2009) observe a decline in reelection rates, partly attributable to the evolving dynamics introduced by redistricting. Nonetheless, districts and political contexts vary: Cox and Katz (Reference Cox and Katz2002) and Murphy and Yoshinaka (Reference Murphy and Yoshinaka2009) detail how challengers’ strategic responses can alter the incumbency landscape, with some incumbents successfully adapting through political skill. Cox and Katz (Reference Cox and Katz2002) also link Supreme Court rulings to shifts in incumbency advantages, demonstrating how legal interpretations of redistricting standards can influence political tenure. Desposato and Petrocik (Reference Desposato and Petrocik2003) highlight how new voters brought in through redistricting challenge incumbents’ electoral safety, while Hood and McKee (Reference Hood and McKee2010) focus on how changing district demographics can weaken incumbents’ connection to their voters, increasing electoral competition and unpredictability. Additionally, as Grofman and Brunell (Reference Grofman, Brunell and Balderisi2005) show in their discussion of the “dummymander,” ambitious partisan remaps can backfire by overextending a party’s support and inadvertently turning presumed gains into unexpected losses.

The way districts are drawn influences not only who runs and wins elections, but also which groups are ultimately represented in government. This dynamic process affects political participation across multiple levels and plays a crucial role in either fostering or hindering equitable representation. As the debate continues over optimal district design, understanding the nuanced impacts of redistricting on voter turnout and political engagement remains vital for developing effective electoral policies.

Redistricting under the Voting Rights Act particularly shapes electoral representation through the creation of majority–minority districts. These districts aim to improve minority representation by ensuring sufficient concentrations of minority voters capable of electing candidates of their choice. However, this approach raises complex discussions about balancing substantive and descriptive representation (see, e.g., Cameron, Epstein, and O’Halloran Reference Cameron, Epstein and O’Halloran1996; Epstein et al. Reference Epstein, Herron, O’Halloran and Park2007; Swain Reference Swain1993; Tate Reference Tate2004). Achieving this balance is important in ensuring that minority groups are both numerically represented and able to influence policy through elected officials. Lublin (Reference Lublin1997) further advocates for a harmonious approach that combines both forms of representation, emphasizing that effective minority representation involves electing candidates who reflect their demographic characteristics and advocate for their interests (also see Canon Reference Canon1999).

The physical shape of districts also affects representational responsiveness. Barabas and Jerit (Reference Barabas and Jerit2004) argue that more compact districts enhance the electoral influence of minority populations by facilitating mobilization and advocacy efforts. Bowen (Reference Bowen2014) examines how district shape relates to communication and accountability between representatives and voters, suggesting that more geographically cohesive districts tend to improve responsiveness. This ongoing debate considers whether district shape should be prioritized alongside demographic considerations in redistricting processes.

Despite efforts to boost minority representation, Bullock (Reference Bullock2010) and Hill (Reference Hill1995) warn of potential “bleaching” effects, where the concentration of minority voters in majority–minority districts may reduce diversity in neighboring districts and diminish overall minority influence. Cameron, Epstein, and O’Halloran (Reference Cameron, Epstein and O’Halloran1996) and Epstein et al. (Reference Epstein, Herron, O’Halloran and Park2007) note paradoxes within minority representation efforts, observing that while creating majority–minority districts can elevate minority voices, it can also lead to unintended political shifts and strategic realignments. For example, some majority-Black districts may benefit other demographic groups – such as white voters – as noted by Canon (Reference Canon1999). Boatright (Reference Boatright2004) and Crespin (Reference Crespin2010) highlight how these shifts often compel congressional representatives to adapt their outreach and engagement strategies, reflecting the dynamic and evolving impact of redistricting on American politics.

Beyond minority districts, it is essential to consider how redistricting impacts overall voter engagement and participation across communities. The design and demographic composition of districts influence internal political dynamics within minority populations and shape voters’ perceptions of their districts – affecting their sense of efficacy and motivation to participate. These factors, in turn, influence electoral competitiveness. As the discussion progresses, it becomes clear that the physical boundaries of districts and the characteristics of the populations within them have tangible effects on voter turnout, with implications that extend beyond minority communities to the electorate as a whole.

Research by Hayes and McKee (Reference Hayes and McKee2009) and Hunt (Reference Hunt2018) indicates that redistricting often has a depressant effect on voter turnout, especially immediately following boundary changes. Voters may feel less connected or informed about their new incumbents, leading to reduced participation. Conversely, studies by Barreto, Segura, and Woods (Reference Barreto, Segura and Woods2004), Hayes and McKee (Reference Hayes and McKee2012), and Fraga (Reference Fraga2016) reveal that the impact of redistricting on turnout varies across different communities and demographics, suggesting that individual and community characteristics significantly mediate the effect of redistricting on voter motivation and engagement. Henderson, Sekhon, and Titiunik (Reference Henderson, Sekhon and Titiunik2016) emphasize the importance of geographic and demographic factors, such as the location of minority populations within districts and local social dynamics, in shaping turnout responses. Fraga (Reference Fraga2016) finds that the presence of co-ethnic candidates can increase engagement among minority voters like African Americans, though in some majority-Latino districts, turnout may be dampened – reflecting the complex interplay of community identity, district design, and voter motivation.

The influence of district shape has also been explored by Ladewig (Reference Ladewig2018) and Winburn and Wagner (Reference Winburn and Wagner2010). Ladewig advocates for more compact districts, arguing that such boundaries improve communication between representatives and constituents, fostering higher voter participation. Winburn and Wagner (Reference Winburn and Wagner2010) examine how geographic cohesion and logical district boundaries influence voters’ willingness to engage, finding that districts with community-oriented shapes tend to experience higher recall of the candidates in their House race. These studies highlight that, beyond demographic composition, the physical configuration of districts plays a fundamental role in promoting electoral engagement at the community and individual levels.

In summary, redistricting influences various aspects of electoral politics, including candidate entry, electoral competitiveness, voter participation, and the representation of different communities. Existing research offers differing evaluations of its role in polarization and incumbency, but there is general acknowledgment of its capacity to impact political dynamics. Understanding the effects of district design – both in terms of demographic makeup and geographic characteristics – can inform discussions on electoral reform and policymaking.

Future research directions in redistricting research

The influence of redistricting extends beyond administrative procedures, fundamentally affecting electoral competitiveness, party dynamics, and public trust. Although much scholarly attention has focused on its role in creating partisan advantage and entrenching incumbency in general elections, less is understood about how redistricting shapes the earliest stages of the electoral cycle – namely, primary elections, which often determine the eventual candidates for legislative offices. Given that primaries are typically decisive in candidate selection, particularly in heavily partisan districts, understanding how various redistricting approaches influence intra-party contests is essential. Filling this gap presents a valuable avenue for empirical research, as it can reveal insights about candidate diversity, intra-party rivalry, and voter engagement – elements that directly influence democratic accountability and the quality of representation.

Primary elections serve as the initial battleground where parties endorse their candidates and set ideological trajectories for general contests. The way districts are drawn can significantly influence the competitiveness of these races, but the existing literature offers limited systematic analysis. A key question is whether reforms such as independent commissions foster more competitive primaries by expanding candidate pools and reducing incumbent advantages. For instance, do districts designed under nonpartisan guidelines attract a broader array of challengers, thus encouraging ideological diversity? Conversely, partisan gerrymandering may produce “safe” districts that dissuade challengers and reinforce incumbent dominance, thereby narrowing ideological representation within parties. Further research should examine the relationship between redistricting methods and intra-party dynamics – such as voter turnout within primaries, candidate diversity, and the level of intra-party polarization. Are districts drawn by independent bodies associated with more challenges to incumbents, and do such contests lead to greater ideological variation? Addressing these questions empirically will clarify whether redistricting can serve as a tool to improve intra-party accountability and whether it enhances the overall responsiveness of candidates to voter preferences during this critical stage of electoral politics.

Redistricting-driven incumbent contests offer a concrete lens on how mapmaking reshapes primary competition. Ashton, Crespin, and McKee (Reference Ashton, Crespin and McKee2023) show these duels mostly arise from reapportionment losses and partisan line-drawing and feature large shares of new constituents, heightening incumbent vulnerability. Case studies and survey work (see, e.g., Hood and McKee Reference Hood and McKee2023; Hood, Hughes, and McKee Reference Hood, Hughes and McKee2025) indicate outcomes hinge less on retained constituents and more on partisan cues and candidate-level dynamics – e.g., Trump endorsements or alignment with the MAGA wing in Republican primaries, and descriptive representation, ideological fit, or scandals in Democratic contests. Together, this evidence suggests institutional design and partisan signaling shape whether primaries become competitive and which challengers succeed, highlighting the need to link redistricting reforms to intra-party contestation.

Beyond the tangible effects on candidate entry and competition, recent research demonstrates how redistricting profoundly influences public perceptions of electoral fairness and the legitimacy of democratic institutions. While many Americans lack detailed knowledge of redistricting institutions and procedures (see, e.g., Cooper et al. Reference Cooper, Huffmon, Knotts and McKee2024; Fougere, Ansolabehere, and Persily Reference Fougere, Ansolabehere and Persily2010; Panagopoulos Reference Panagopoulos2013), high-profile reforms and controversies influence perceptions of electoral fairness. Williamson and Justwan (Reference Williamson and Justwan2025) find that perceiving redistricting as partisan reduces system support, whereas independent commissions lower perceived gerrymandering and improve evaluations of the democratic process. Absent specific knowledge, partisanship structures opinions: supporters of both parties favor reforms that advance their party’s prospects, and experiments show greater support when reforms are framed as benefiting one’s party (Biggers Reference Biggers2019; Biggers and Bowler Reference Biggers and Bowler2022). Strong partisans may accept measures that weaken electoral fairness if they believe it helps their side (McCarthy Reference McCarthy2022), and McLaughlin (Reference McLaughlin2025) shows partisan self-interest often drives reform preferences.

However, the link between partisanship and fairness perceptions is nuanced. Political actors are not motivated solely by partisanship (Virgin Reference Virgin2023), and priming procedural fairness can temper partisan biases: perceived unfairness reduces support for reforms, while fairness cues can increase support irrespective of party (Biggers and Bowler Reference Biggers and Bowler2023). Although party labels raise the likelihood of choosing partisan-favoring maps, a majority across parties prefer nonpartisan or fair maps when presented explicitly (McCarthy Reference McCarthy2022). Overall, this emerging line of work illustrates that institutional design choices shape not only electoral outcomes but also public evaluations of democratic legitimacy.

Citizens’ confidence in the electoral process hinges on their belief that districts are drawn equitably and transparently (Fougere, Ansolabehere, and Persily Reference Fougere, Ansolabehere and Persily2010; Panagopoulos Reference Panagopoulos2013). Increasingly Americans find gerrymandering to be a major problem and think it should be illegal (Hayes Reference Hayes2025). When voters perceive legislative districts as drawn fairly, and representatives as legitimately elected, higher levels of electoral participation and institutional trust tend to follow, even though evaluations of fairness are often filtered through partisan considerations and perceptions of which groups are advantaged (McLaughlin Reference McLaughlin2025; Tolbert, Smith, and Green Reference Tolbert, Smith and Green2009; VanderMolen and Milyo Reference VanderMolen and Milyo2017). Conversely, perceptions of manipulation and unfairness contribute to political apathy, disengagement, and erosion of democratic norms (Williamson and Justwan Reference Williamson and Justwan2025). Recognizing this, future research should investigate the effects of different redistricting methods on long-term institutional support, building on work that links institutional design, transparency, and public confidence in the process (Cooper et al. Reference Cooper, Huffmon, Knotts and McKee2024; Panagopoulos Reference Panagopoulos2013).

Longitudinal comparative studies could elucidate whether jurisdictions with independent, transparent redistricting processes sustain higher levels of civic engagement and institutional trust over time (Panagopoulos Reference Panagopoulos2013; VanderMolen and Milyo Reference VanderMolen and Milyo2017). Additionally, experimental studies and survey-based research could test how perceived fairness influences not only voting behavior but also voluntary compliance with electoral laws and willingness to participate in civic life beyond voting, while distinguishing between preferences over process and outcomes (see, e.g., McLaughlin et al. Reference McLaughlin, Olson, Barron, Ashton, Blum, Finocchiaro and Crespin2025; Tolbert, Smith, and Green Reference Tolbert, Smith and Green2009). Analyzing these mechanisms empirically will advance understanding of how procedural fairness in redistricting fosters more resilient democratic norms and community cohesion, particularly in an increasingly polarized political environment (Cooper et al. Reference Cooper, Huffmon, Knotts and McKee2024; Williamson and Justwan Reference Williamson and Justwan2025).

Lastly, American politics is currently highly nationalized (Carson, Sievert, and Williamson Reference Carson, Sievert and Williamson2024); voters care more about which party controls the federal government than about which individual represents them in Congress. This shift has important implications both for how citizens think redistricting should be done and for how redistricting shapes election outcomes. As illustrated in the Texas–California example discussed at the outset of our work, are citizens supportive of engaging in aggressive party gerrymanders within their state to counter the other party’s gerrymanders in other states? While this would make control of the U.S. House of Representatives more competitive, it would likely come at the expense of district-level competition and the overall representativeness of outcomes at the statewide level. Future research can hopefully shed more light on these issues, specifically, as well as attitudes toward and the effect of different redistricting practices, broadly.