Designing Tests of the Supreme Court and the Separation of Powers

Abstract

While rational choice models of Supreme Court decisionmaking have enhanced our appreciation for the separation of powers built into the Madisonian Constitutional design, convincing empirical support for a Separation-of-Powers (SOP) constraint on justices’ behavior has been elusive. We apply a standard spatial voting model to identify circumstances in which Attitudinalist and SOP predictions about justices’ behavior diverge. Our reconsideration of the theory indicates that prior efforts to test quantitatively the two models have failed to select out cases for which the two models’ predictions do not differ. While our more focused test offers a fairer test of the SOP constraint, the results strongly reject the SOP model. Nonetheless, our analysis provides leverage on this issue by: (1) delineating and executing necessary research design protocols for crafting a critical test of the SOP model; and (2) rejecting the two exogenously fixed alternative SOP models and suggesting avenues for future research.