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Partisanship, Ideology, and Senate Voting on Supreme Court Nominees


  • Originally prepared for presentation at the Conference on Empirical Legal Studies, University of Texas School of Law, Austin, Texas, October 27–28, 2006. I thank Ted Eisenberg, Meredith Fowlie, Matt Golder, Jeff Segal, Joel Simmons, Jeff Staton, and Chad Westerland for useful discussions and suggestions, and an anonymous reviewer for an unusually thorough and insightful review. I am especially grateful to Fred Boehmke, Katie Drake, Eric Lawrence, and David Primo, each of whom patiently and helpfully shared their considerable methodological expertise with me.

*J. Ira and Nicki Harris Professor of Social Science, Department of Political Science, University of Michigan, 7764 Haven Hall, Ann Arbor, MI 48109-1045; email:


Ideological concerns play a major role in determining whether a senator will vote to confirm or reject a Supreme Court nominee. Much less is understood, however, about the effects of partisanship on confirmation votes. This study investigates two aspects of partisanship: first, whether confirmation voting has become more partisan over time, even when controlling for other factors, including ideology; and second, whether partisanship modifies the influence of ideology. The results demonstrate that partisanship has played an increasing role over time and that the effects of ideology are contingent on partisanship.