Are Supreme Court Nominations a Move-the-Median Game?

Abstract

We conduct a theoretical and empirical re-evaluation of move-the-median (MTM) models of Supreme Court nominations—the one theory of appointment politics that connects presidential selection and senatorial confirmation decisions. We develop a theoretical framework that encompasses the major extant models, formalizing the tradeoff between concerns about the location of the new median justice versus concerns about the ideology of the nominee herself. We then use advances in measurement and scaling to place presidents, senators, justices, and nominees on the same scale, allowing us to test predictions that hold across all model variants. We find very little support for MTM theory. Senators have been much more accommodating of the president’s nominees than MTM theory would suggest—many have been confirmed when the theory predicted they should have been rejected. These errors have been consequential: presidents have selected many nominees who are much more extreme than MTM theory would predict. These results raise serious questions about the adequacy of MTM theory for explaining confirmation politics and have important implications for assessing the ideological composition of the Court.