Does the Attitudinal Model Explain Unanimous Reversals?

There is little doubt that the political attitudes of the justices on the Supreme Court have a significant impact on many outcomes adopted by the Court. But a third or more of Supreme Court decisions are unanimous, and in more than a fifth of their cases every year the Supreme Court unanimously reverses the decision below. The Attitudinal Model suggests that the reason for unanimity is that the political policy made by the court below is “extreme” when compared to the ideological range of the entire Supreme Court. We test the basic claim of the most prominent proponents of the Attitudinal Model that the political preferences of the justices provide a complete explanation for all of their decisions, including those decided unanimously. We find that none of the predictions of the Attitudinal Model are supported. Thus, while the ideology of the justices may drive many of their decisions, the Attitudinal Model does not provide an adequate explanation for unanimous decisions.