The Electoral Costs of Party Loyalty in Congress


  • This is a substantially revised version of a paper presented at the 2006 annual meeting of the Midwest Political Science Association. The authors wish to thank Ben Bishin, Justin Buchler, Stanley Feldman, Jeff Grynaviski, Gary Jacobson, Phil Paolino, Doug Roscoe, the political science colloquium at the University of Miami, and three anonymous referees for comments; Ellen Key, David Perkins, and Andrew Sidman for research assistance; and the Dirksen Center for its financial support of this project.

Jamie L. Carson is Associate Professor of Political Science, The University of Georgia, 104 Baldwin Hall, Athens, GA 30602-1615 ( Gregory Koger is Associate Professor of Political Science, University of Miami, 314 Jenkins Building, Coral Gables, FL 33124-6534 ( Matthew J. Lebo is Associate Professor of Political Science, Stony Brook University, SBS S-749, Stony Brook, NY 11794-4392 ( Everett Young is a 2009 PhD in political science from Stony Brook University, Stony Brook, NY 11794-4392 (


To what extent is party loyalty a liability for incumbent legislators? Past research on legislative voting and elections suggests that voters punish members who are ideologically “out of step” with their districts. In seeking to move beyond the emphasis in the literature on the effects of ideological extremity on legislative vote share, we examine how partisan loyalty can adversely affect legislators' electoral fortunes. Specifically, we estimate the effects of each legislator's party unity—the tendency of a member to vote with his or her party on salient issues that divide the two major parties—on vote margin when running for reelection. Our results suggest that party loyalty on divisive votes can indeed be a liability for incumbent House members. In fact, we find that voters are not punishing elected representatives for being too ideological; they are punishing them for being too partisan.