Assessing the Stability of the Rule of Four on the U.S. Supreme Court

Abstract

Most research on the U.S. Supreme Court treats the Rule of Four as a fixed agenda-setting norm to which justices faithfully adhere. In this paper, we investigate the stability of the Rule of Four and suggest that there are circumstances under which the Rule of Four is violated. We argue that these violations are tied to the degree of ideological heterogeneity on the Court. Applying an existing theory of institutional stability (Barbera and Jackson, 2004), we connect agenda-setting procedures directly to the ideological heterogeneity of the justices on a given Court. We investigate hypothetical ideological configurations as well as the 1937-2006 terms of the Court and find that the Rule of Four is rarely stable. Only when a majority coalition, considering an ideologically incongruent lower court decision, possesses high intra-coalition ideological homogeneity, is the Rule of Four stable.