Party Polarization in Congress: A Social Networks Approach

We measure polarization in the United States Congress using the network science concept of modularity. Modularity provides a conceptually-clear measure of polarization that reveals both the number of relevant groups and the strength of inter-group divisions without making restrictive assumptions about the structure of the party system or the shape of legislator utilities. We show that party influence on Congressional blocs varies widely throughout history, and that existing measures underestimate polarization in periods with weak party structures. We demonstrate that modularity is a significant predictor of changes in majority party and that turnover is more prevalent at medium levels of modularity. We show that two variables related to modularity, called `divisiveness' and `solidarity,' are significant predictors of reelection success for individual House members. Our results suggest that modularity can serve as an early warning of changing group dynamics, which are reflected only later by changes in party labels.

[1]  Stuart A. Rice,et al.  The Identification of Blocs in Small Political Bodies , 1927, American Political Science Review.

[2]  A. Downs.  An Economic Theory of Political Action in a Democracy , 1957, Journal of Political Economy.

[3]  A. Downs.  An Economic Theory of Democracy , 1957 .

[4]  D. Truman,et al.  The congressional party : a case study , 1960 .

[5]  Ruth C. Silva,et al.  Making votes count , 1963 .

[6]  M. Duverger.  Political Parties Their Organization and Activity in the Modern State , 1964 .

[7]  M. Olson,et al.  The Logic of Collective Action , 1965 .

[8]  Walter Dean Burnham,et al.  Critical Elections: And the Mainsprings of American Politics , 1970 .

[9]  Brian W. Kernighan,et al.  An efficient heuristic procedure for partitioning graphs , 1970, Bell Syst. Tech. J..

[10]  M. Watts,et al.  Legislative Roll-Call Analysis , 1971 .

[11]  David R. Mayhew.  Congress: The Electoral Connection , 1975 .

[12]  K. Shepsle.  Institutional Arrangements and Equilibrium in Multidimensional Voting Models , 1979 .

[13]  John R. Petrocik.  Party Coalitions: Realignment and the Decline of the New Deal Party System , 1981 .

[14]  G. Jacobson,et al.  The Politics of Congressional Elections , 1983 .

[15]  The Breakdown of Democratic Party Organization, 1940-1980 , 1985 .

[16]  W. Riker.  The art of political manipulation , 1987 .

[17]  T. L. Schwartz.  The Logic of Collective Action , 1986 .

[18]  B. Weingast,et al.  The Institutional Foundations of Committee Power , 1987, American Political Science Review.

[19]  R. Huckfeldt,et al.  Networks in Context: The Social Flow of Political Information , 1987, American Political Science Review.

[20]  K. Koford,et al.  Dimensions in Congressional Voting , 1989, American Political Science Review.

[21]  Peter J. Rousseeuw,et al.  Finding Groups in Data: An Introduction to Cluster Analysis , 1990 .

[22]  Keith Krehbiel,et al.  Information and legislative organization , 1991 .

[23]  Dennis F. Kinsey,et al.  The Reasoning Voter: Communication and Persuasion in Presidential Campaigns , 1993 .

[24]  David W. Rohde.  Parties and leaders in the postreform house , 1991 .

[25]  Mathew D. McCubbins,et al.  Legislative Leviathan: Party Government in the House , 1993 .

[26]  Ivars Peterson,et al.  Making votes count , 1963 .

[27]  Paul S. Herrnson,et al.  Congressional Elections: Campaigning at Home and in Washington , 1995 .

[28]  John H. Aldrich.  Why parties? : the origin and transformation of political parties in America , 1995 .

[29]  Patrick J. F. Groenen,et al.  Modern Multidimensional Scaling: Theory and Applications , 2003 .

[30]  Nolan McCarty,et al.  Income redistribution and the realignment of American politics , 1997 .

[31]  K. T. Poole,et al.  Congress: A Political-Economic History of Roll Call Voting , 1997 .

[32]  Janet M. Martin.  Congress: A Political-Economic History of Roll Call Voting . By Keith T. Poole and Howard Rosenthal. (New York: Oxford University Press, 1997. Pp. 297. $85.00.) , 1998 .

[33]  Nancy B. Shulock.  Legislatures: Rational Systems or Rational Myths? , 1998 .

[34]  Keith Krehbiel,et al.  Pivotal Politics: A Theory of U.S. Lawmaking , 1998 .

[35]  G. Jacobson,et al.  The Logic of American Politics , 1999 .

[36]  Sarah Binder.  The Dynamics of Legislative Gridlock, 1947–96 , 1999, American Political Science Review.

[37]  P. Groenen,et al.  Modern Multidimensional Scaling: Theory and Applications , 1999 .

[38]  James M. Snyder,et al.  Estimating Party Influence in Congressional Roll-Call Voting , 2000 .

[39]  Guohua Pan,et al.  Local Regression and Likelihood , 1999, Technometrics.

[40]  J. R. Bond,et al.  Polarized politics : Congress and the President in a partisan era , 2000 .

[41]  Howard Rosenthal,et al.  THE HUNT FOR PARTY DISCIPLINE IN CONGRESS # , 2001 .

[42]  M. Wand.  Local Regression and Likelihood , 2001 .

[43]  Nolan McCarty,et al.  The Hunt for Party Discipline in Congress , 2001, American Political Science Review.

[44]  K. T. Poole,et al.  On Measuring Partisanship in Roll Call Voting:The U.S. House of Representatives, 1877-1999 , 2002 .

[45]  D. Brady,et al.  Out of Step, Out of Office: Electoral Accountability and House Members' Voting , 2002, American Political Science Review.

[46]  Mark E. J. Newman,et al.  The Structure and Function of Complex Networks , 2003, SIAM Rev..

[47]  M E J Newman,et al.  Fast algorithm for detecting community structure in networks. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[48]  Georg Vanberg,et al.  Veto Players: How Political Institutions Work , 2004, The Journal of Politics.

[49]  M E J Newman,et al.  Finding and evaluating community structure in networks. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[50]  John H. Aldrich,et al.  Examining Congress with a Two-Dimensional Political Space , 2004 .

[51]  Joshua D. Clinton,et al.  The Statistical Analysis of Roll Call Data , 2004, American Political Science Review.

[52]  M. Fiorina,et al.  Culture War?: The Myth of a Polarized America , 2004 .

[53]  Keith T. Poole,et al.  Spatial Models of Parliamentary Voting , 2005 .

[54]  G. Jacobson.  Polarized Politics and the 2004 Congressional and Presidential Elections , 2005 .

[55]  Casey M. Warmbrand,et al.  A Network Analysis of Committees in the U.S. House of Representatives , 2013, Proceedings of the National Academy of Sciences of the United States of America.

[56]  S. McClurg,et al.  The Mobilization of Core Supporters: Campaigns, Turnout, and Electoral Composition in United States Presidential Elections , 2005 .

[57]  Leon Danon,et al.  Comparing community structure identification , 2005, cond-mat/0505245.

[58]  M. Newman,et al.  Finding community structure in networks using the eigenvectors of matrices. , 2006, Physical review. E, Statistical, nonlinear, and soft matter physics.

[59]  Gábor Csárdi,et al.  The igraph software package for complex network research , 2006 .

[60]  M E J Newman,et al.  Modularity and community structure in networks. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[61]  James H. Fowler,et al.  Legislative cosponsorship networks in the US House and Senate , 2006, Soc. Networks.

[62]  Andrew Gelman,et al.  Data Analysis Using Regression and Multilevel/Hierarchical Models , 2006 .

[63]  Matthieu Latapy,et al.  Computing Communities in Large Networks Using Random Walks , 2004, J. Graph Algorithms Appl..

[64]  J. Jenkins.  Setting the Agenda: Responsible Party Government in the House of Representatives , 2006, The Journal of Politics.

[65]  Mason A. Porter,et al.  Community Structure in the United States House of Representatives , 2007, ArXiv.

[66]  Randall Strahan,et al.  Setting the Agenda: Responsible Party Government in the U.S. House of Representatives , 2006, Perspectives on Politics.

[67]  G. Jacobson,et al.  A Divider, Not a Uniter: George W. Bush and the American People, The 2006 Election and Beyond , 2006 .

[68]  Scott D. McClurg,et al.  The Electoral Relevance of Political Talk: Examining Disagreement and Expertise Effects in Social Networks on Political Participation , 2006 .

[69]  Alan L. Olmstead,et al.  Historical Statistics of the United States , 2006 .

[70]  J. Horowitz,et al.  PARTY POLARIZATION IN AMERICAN POLITICS: Characteristics, Causes, and Consequences , 2006 .

[71]  K. T. Poole,et al.  Polarized America: The Dance of Ideology and Unequal Riches , 2006 .

[72]  J. Fowler.  Connecting the Congress: A Study of Cosponsorship Networks , 2006, Political Analysis.

[73]  Steven S. Smith.  Party Influence in Congress , 2007 .

[74]  S. Levin,et al.  The dynamics of political polarization , 2021, Proceedings of the National Academy of Sciences.

[75]  S. Fortunato,et al.  Resolution limit in community detection , 2006, Proceedings of the National Academy of Sciences.

[76]  Stanley Wasserman,et al.  Social Network Analysis: Methods and Applications , 1994, Structural analysis in the social sciences.

[77]  John H. Aldrich.  The Logic of Conditional Party Government: Revisiting the Electoral Connection , 2008 .

[78]  Jean-Loup Guillaume,et al.  Fast unfolding of communities in large networks , 2008, 0803.0476.

[79]  B. Grofman,et al.  Cycles in American National Electoral Politics, 1854–2006: Statistical Evidence and an Explanatory Model , 2008, American Political Science Review.

[80]  M. Fiorina,et al.  Political Polarization in the American Public , 2008 .

[81]  Amanda L. Traud,et al.  Community Structure in Congressional Cosponsorship Networks , 2007, 0708.1191.

[82]  Ulrik Brandes,et al.  On Modularity Clustering , 2008, IEEE Transactions on Knowledge and Data Engineering.

[83]  Joseph Hilbe,et al.  Data Analysis Using Regression and Multilevel/Hierarchical Models , 2009 .

[84]  V. Traag,et al.  Community detection in networks with positive and negative links. , 2008, Physical review. E, Statistical, nonlinear, and soft matter physics.

[85]  Hans Noel,et al.  Partisan Webs: Information Exchange and Party Networks , 2009, British Journal of Political Science.

[86]  Santo Fortunato,et al.  Community detection in graphs , 2009, ArXiv.

[87]  P. Mucha,et al.  Spectral tripartitioning of networks. , 2008, Physical review. E, Statistical, nonlinear, and soft matter physics.

[88]  Mason A. Porter,et al.  Communities in Networks , 2009, ArXiv.

[89]  Benjamin H. Good,et al.  Performance of modularity maximization in practical contexts. , 2009, Physical review. E, Statistical, nonlinear, and soft matter physics.

[90]  K. Stovel,et al.  Network Analysis and Political Science , 2011 .

[91]  D. Lazer.  Networks in Political Science: Back to the Future , 2011, PS: Political Science & Politics.