The Creation of an Endangered Species

The Creation of an Endangered Species: Party Nonconformists of the U.S. Senate* Richard Fleisher Fordham University Jon R. Bond Texas A&M University Party nonconformists--that is, moderate to conservative Democrats and moderate to liberal Republicans who had policy preferences different from the mainstream of their party--have largely disappeared from the Senate. As nonconformists disappeared from both parties, each caucus became less ideologically diverse and congressional parties polarized. Much of the research on party polarization in Congress has focused on the House and on the realignment in the South that led to the demise of conservative Southern Democrats. Yet we show that there are parallel trends of escalating partisanship in both parties in both the House and Senate. The explanations of why Senate parties polarized and why Republican nonconformists have disappeared, however, are less clear. Part of the explanation of polarization in the House applies to the Senate--the most likely cause is electoral and electoral changes in the South provide an answer for the disappearance of nonconformist Democrats. But since state boundaries are not subject to partisan gerrymandering and since moderate and liberal Republicans have also disappeared, there must be additional electoral processes that produced more homogeneous parties in the Senate. This paper seeks to provide a more complete understanding of how and why Senate parties polarized. We find: 1. Partisan nonconformists were elected disproportionately from states that favor the other party-i.e., nonconformists Democrats tend to come from “red” states and nonconformists Republicans tend to come from “blue” states. 2. The ability of a party’s candidates to win on the other party’s turf has changed over time, but this change has not affected both parties equally. In particular, Democrats’ ability to hold seats in red and competitive states has declined since the early 1980s, while Republicans have maintained their ability to hold Senate seats in blue states and they are more successful in competitive states. 3. When a party does win on the other party’s turf, the likelihood of electing a mainstream partisan has increased over time. Moderate and conservative Democrats have disappeared because there are just fewer Democrats elected in red and competitive states. Republican success in blue and competitive states has not declined, but nonconformist Republicans have disappeared because mainstream Republicans can win in states that once elected moderates. 4. The ability to elect mainstream Republicans in blue and competitive states is due in part to changes in Senate electorates and the preferences of Republican voters. *We are happy to acknowledge support from the Departments of Political Science at Fordham University and Texas A&M University. We are grateful for the research assistance of Nathan Ilderton, Sarah Kessler, and Jose Villalobos.