Cameron and Kastellec 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. They 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. They then use advances in measurement and scaling to place presidents, senators, justices, and nominees on the same scale, allowing a test of predictions that hold across all model variants.

Their findings offer 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.

Charles Cameron is Professor of Politics and Public Affairs and John Kastellec is Associate Professor of Politics at Princeton University. Both are CSDP Faculty Associates.