¹ David R. Mayhew, Divided We Govern: Party Control, Lawmaking, and Investigations, 1946–1990 (New Haven, Conn.: Yale University Press, 1991).

² Austin Ranney, The Doctrine of Responsible Party Government (Champaign: University of Illinois Press, 1954).

³ V. O. Key Jr, Politics, Parties, and Pressure Groups (New York: Crowell, 1942); and Randall Ripley, Majority Party Leadership in Congress (Boston, Mass.: Little Brown, 1969).

⁴ Lloyd Cutler, ‘Some Reflections about Divided Government’, Presidential Studies Quarterly, 17 (1988), 485–92; Morris P. Fiorina, Divided Government (Boston, Mass.: Allyn and Bacon, 1996); and James Sundquist, ‘Needed: A Political Theory for the New Era of Coalition Government in the United States’, Political Science Quarterly, 103 (1988), 613–35.

⁵ Mayhew, Divided We Govern.

⁶ David R. Mayhew, Divided We Govern: Party Control, Lawmaking, and Investigations, 1946–2002, 2nd edn (New Haven, Conn.: Yale University Press, 2005).

⁷ Sarah A. Binder, ‘The Dynamics of Legislative Gridlock, 1947–1996’, American Political Science Review, 93 (1999), 519–33; Sarah A. Binder, Stalemate: Causes and Consequences of Legislative Gridlock (Washington, D.C.: The Brookings Institution, 2003); John J. Coleman, ‘Unified Government, Divided Government, and Party Responsiveness’, American Political Science Review, 93 (1999), 821–35; and George C. Edwards III and Andrew Barrett, ‘Presidential Agenda Setting in Congress’, in Jon R. Bond and Richard Fleisher, eds, Polarized Politics: Congress and the President in a Partisan Era (Washington, D.C.: CQ Press, 2000), pp. 109–33.

⁸ Keith Krehbiel, ‘Institutional and Partisan Sources of Gridlock: A Theory of Divided and Unified Government’, Journal of Theoretical Politics, 8 (1996), 7–40; Keith Krehbiel, Pivotal Politics (Chicago: University of Chicago Press, 1998); David Brady and Craig Volden, Revolving Gridlock (Boulder, Colo.: Westview, 1998); and Fang-Yi Chiou and Lawrence S. Rothenberg, ‘When Pivotal Politics Meets Partisan Politics’, American Journal of Political Science, 47 (2003), 503–22.

⁹ Binder, Stalemate; Jon R. Bond and Richard Fleisher, ‘Polarized Politics: Does It Matter?’, in Bond and Fleisher, eds, Polarized Politics, pp. 186–200; and David R. Jones, ‘Party Polarization and Legislative Gridlock’, Political Research Quarterly, 54 (2001), 125–41.

¹⁰ Bond and Fleisher, ‘Polarized Politics’, p. 188.

¹¹ Binder, Stalemate, p. 35.

¹² Mayhew, Divided We Govern: 1946–2002, 2nd edn, p. 202.

¹³ Samuel Kernell, ‘Facing an Opideal Point Congress: The President’s Strategic Circumstance’, in Gary W. Cox and Samuel Kernell, eds, The Politics of Divided Government (Boulder, Colo.: Westview, 1991), pp. 87–112; Krehbiel, Pivotal Politics, p. 26; Brady and Volden, Revolving Gridlock, p. 43; Chiou and Rothenberg, ‘When Pivotal Politics Meets Partisan Politics’, p. 504; and George Tsebelis, Veto Players (Princeton, N.J.: Princeton University Press, 2002), pp. 165–7.

¹⁴ Krehbiel, Pivotal Politics, p. 5.

¹⁵ Tsebelis, Veto Players; Thomas H. Hammond and Gary J. Miller, ‘The Core of the Constitution’, American Political Science Review, 81 (1987), 1115–74; and William H. Riker, ‘The Justification of Bicameralism’, International Political Science Review, 13 (1992), 101–16; and George Tsebelis and Jeanette Money, Bicameralism (New York: Cambridge University Press, 1997).

¹⁶ Tsebelis, Veto Players, p. 6.

¹⁷ E. E. Schattschneider, Party Government (New York: Farrar and Rinehart, 1942).

¹⁸ Schattschneider, Party Government, pp. 89–90.

¹⁹ Mayhew, Divided We Govern: 1946–2000, 2nd edn, pp. 220–1.

²⁰ Krehbiel, ‘Institutional and Partisan Sources of Gridlock’; Krehbiel, Pivotal Politics; Brady and Volden, Revolving Gridlock; and Chiou and Rothenberg, ‘When Pivotal Politics Meets Partisan Politics’.

²¹ Tsebelis, Veto Players, p. 19.

²² Keith T. Poole, ‘Changing Minds? Not in Congress’, http://pooleandrosenthal.com/chminds.pdf, p. 7.

²³ James MacGregor Burns, The Deadlock of Democracy (Englewood Cliffs, N.J.: Prentice-Hall, 1963); Keith T. Poole and Howard Rosenthal, Congress: A Political Economic History of Roll Call Voting (New York: Oxford University Press, 1997), p. 48; and Keith T. Poole, Spatial Models of Parliamentary Voting (New York: Cambridge University Press, 2005), pp. 14–15.

²⁴ Paul Frymer, ‘Ideological Consensus within Divided Government’, Political Science Quarterly, 109 (1994), 287–311.

²⁵ Tsebelis, Veto Players; Hammond and Miller, ‘The Core of the Constitution’; Riker, ‘The Justification of Bicameralism’; and Tsebelis and Money, Bicameralism.

²⁶ Krehbiel’s model is likely to be acameral, rather than unicameral, because of the fictitious juxtaposition of the Senate filibuster pivot and the override, including a potential House override, pivot.

²⁷ Poole and Rosenthal, Congress; and Poole, Spatial Models of Parliamentary Voting.

²⁸ In actual congresses, a pivot represents ideal points of a veto player in dimension 1 and another veto player in dimension 2. Imagine a Southern Democrat who is pivotal in the economic dimension but extremely conservative in the social dimension. Even if she opposes a centrist bill on an exclusively social issue, liberals and moderates could support and pass the bill. This exemplifies that she is not a pivot in the social dimension. Thus, different legislators assume veto power in Dimension 1 and Dimension 2 separately. When legislation involves both economic and social issues with considerable importance, both pivots in Dimension 1 and Dimension 2 maintain veto power, hence decreasing the possibility of a passage. This would increase the necessity of moderating the bill. See Tsebelis, Veto Players, pp. 50–1.

²⁹ For instance, when an ideal point of a bill is outside a liberal veto player’s indifference curve, the measure is likely to move the status quo away from the veto player and from the members who are more liberal than her. Thus, when a veto player opposes a bill, adjacent members with more extreme preferences are likely to oppose the measure as well.

³⁰ In a sharp contrast, majority-rule spatial voting games are likely to result in unpredictable and unstable voting outcomes. When there is no one alternative that can defeat other alternatives, there is always an incentive for a new majority coalition to form and defeat the present status quo. See Richard D. McKelvey, ‘Intransitivities in Multidimensional Voting Models and Some Implications for Agenda Control’, Journal of Economic Theory, 12 (1976), 472–82; Richard D. McKelvey, ‘General Conditions for Global Intransitivities in Formal Voting Models’, Econometrica, 47 (1979), 1085–112; and Norman Schofield, ‘The Theory of Dynamic Games’, Review of Economic Studies, 45 (1978), 575–94.

³¹ Mayhew, Divided We Govern: 1946–2000, 2nd edn, pp. 208–13.

³² Sean Q. Kelly, ‘Divided We Govern? A Reassessment’, Polity, 25 (1993), 475–84.

³³ Binder, Stalemate, pp. 37–44.

³⁴ Edwards and Barrett, ‘Presidential Agenda Setting in Congress’.

³⁵ Rescaled score = 120−(original score×5).

³⁶ Binder, Stalemate, notes a similar finding (p. 42).

³⁷ Poole and Rosenthal, Congress, pp. 59–70.

³⁸ This approximates a central ideal point of the ‘Yea’ voters of passed bills. Poole and Rosenthal study policy swing by examining the MWC scores.

³⁹ Americans for Democratic Action, http://www.adaction.org/voting.htm

⁴⁰ There have been debates about a potential bias in the various selection methods of important laws. For bias in the selection of important laws by Mayhew, see Kelly, ‘Divided We Govern?’ and William Howell, Scott Adler, Charles Cameron and Charles Riemann, ‘Divided Government and the Legislative Productivity of Congress, 1945-1994’, Legislative Studies Quarterly, 25 (2000), 285–312. As for bias in laws selected by the ADA, see James M. Snyder Jr, ‘Artificial Extremism in Interest Group Ratings’, Legislative Studies Quarterly, 17 (1992), 319–45; Michael C. Herron, ‘Artificial Extremism in Interest Group Ratings and the Preferences versus Party Debate’, Legislative Studies Quarterly, 24 (1999), 525–42; and Tim Groseclose, Steven Levitt and James M. Snyder Jr, ‘Comparing Interest Group Scores across Time and Chambers: Adjusted ADA Scores for the U.S. Congress’, American Political Science Review, 93 (1999), 33–50. In contrast to the aforementioned scholars, Krehbiel contends that the bias is minimal and has no effect on the inference of the legislators’ preferences; see Keith Krehbiel, ‘Deference, Extremism, and Interest Group Ratings’, Legislative Studies Quarterly, 19 (1994), 61–77. Also, several scholars have found that the ADA ratings are very similar to other interest group ratings and roll-call ratings; see Poole and Rosenthal, Congress; and Brady and Volden, Revolving Gridlock, pp. 116–20. Brady and Volden calculate the average scores of eighteen interest-group ratings for the legislators. The average ratings are greatly correlated with the sole ADA ratings. This indicates that interest groups select similar laws. Poole and Rosenthal find that their dw-nominate scores, which are measured based upon the members’ votes on roll calls, are highly related to the ADA scores. In my study, the ADA measure of the change in policy output shows a significant correlation (r = 0.65) with the MWC measure.

⁴¹ ADA change = ADA policy output_t−ADA policy output_{t −1}.

⁴² MWC change=.

⁴³ As for the filibuster pivot before 1975, the 34th and 67th percentile legislator under Republican and Democratic presidency, respectively.

⁴⁴ Optimal Classification (OC) is a non-parametric scaling method with an assumption of legislators with single-peaked preferences in Euclidean space. The OC scale produces ideal points and cutting planes for the roll-call votes that maximize the number of correctly classified voting decisions. Just as the dw-nominate scores, the OC scores range from −1 to +1 and are comparable among different Congresses. In addition, the OC scores in the House and the Senate are comparable. Poole places the House and Senate in the same space based upon the ideal points of the legislators who served in both the House and Senate. See Poole, Spatial Models of Parliamentary Voting, pp. 192–5.

⁴⁵ I used AutoCAD^® by Autodesk. AutoCAD^® is a design and drafting software for industrial engineering.

⁴⁶ Binder, ‘The Dynamics of Legislative Gridlock, 1947–1996’; Binder, Stalemate; Coleman, ‘Unified Government, Divided Government, and Party Responsiveness’; Krehbiel, Pivotal Politics; and Chiou and Rothenberg, ‘When Pivotal Politics Meets Partisan Politics’.

⁴⁷ James A. Stimson, Public Opinion in America: Moods, Cycles, and Swing (Boulder, Colo.: Westview Press, 1991); and James A. Stimson, 〈http://www.unc.edu/~jstimson/time.html〉.

⁴⁸ As I noted in the previous section, the exploration of the impact of divided government in conditional terms with intra-party and inter-party homogeneity, or with the size of the party, is not an appropriate test for party control of the government. If party control matters, divided government should cause gridlock without any interactive mutation. The influence of divided government in conditional terms with the alignment of legislators’ preferences indicates the influence of individual legislators’ preference rather than party control of the government.

⁴⁹ Edwards and Barrett, ‘Presidential Agenda Setting in Congress’.

⁵⁰ For the variables of Binder’s and Edwards’s measurements, which are ratio variables constructed from grouped data, I model variation with the weighted least squares logistic regression for grouped data (Glogit). The Glogit function accounts for the variation in the denominator for the ratio variables.

⁵¹ Mayhew, Divided We Govern, 1946–2000, 2nd edn, pp. 207–15.

⁵² By examining congresses from 1946 to 1986, Kelly finds a moderate impact of divided government.

⁵³ In contrast, Binder finds an impact of divided government regardless of the salience level of legislative agendas. See Binder, Stalemate, pp. 68–73.

⁵⁴ For both the two variables, the Augmented Dickey–Fuller test and Phillips–Perron test strongly reject the hypothesis of a unit root.

⁵⁵ The variables of winset and divided government are not related (r = 0.17).

⁵⁶ Schattschneider, Party Government.

⁵⁷ The MWC policy change is the difference between the MWC score in the examined congress and the status quo. While the value of the status quo is partially involved in the calculation for the dependent variable, there is a possibility that the status quo could also influence the winset area. The winset area could be potentially affected by the veto players’ propinquity to the status quo, as well as the veto players’ proximity among themselves. However, a preliminary test confirmed that the variables of the MWC policy change and the winset size are not related to the values of the status quo in Dimension 1 or Dimension 2. Thus, the policy shift in the MWC measure and the area of the winset are not confounded with the value of the status quo.

⁵⁸ Poole and Rosenthal, Congress, pp. 53–7.

⁵⁹ Mayhew, Divided We Govern, 1946–2000, 2nd edn, pp. 220–1.