The Effect of Ideology on Supreme Court Judging Over Time: An Influence on the Decline?

Empirical scholars of the United States Supreme Court, Jeffrey Segal and Harold Spaeth have long contended that Supreme Court decisions are based primarily upon the ideological beliefs of the justices, and that ideology alone accounts for the bulk of choices justices make in civil liberties cases. However, recent scholarship demonstrates that this conclusion was exaggerated. But although ideology is not as dominant of a force upon the Court as attitudinal modelers previously thought, it is still an important variable in the judging equation. It most certainly is a statistical predictor. This paper adds two important contributions to the new findings: (1) the role that ideology plays upon the Court is not stable across time and appears to be trending downward; and (2) Segal/Cover scores are a relatively poor explanation of voting behavior and at times are a complete failure. Scholars are encouraged not only to reconsider the way that they conceptualize the force of ideology in the judicial mind, but to also whether Segal/Cover scores are an appropriate independent variable in ideology models.

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The Failure of Instrumentalism: An Analysis of Votes by Conservative Justices on the U.S. Supreme Court in the Area of Core Political Speech.

Abstract: Scholars such as Segal and Spaeth contend that U.S. Supreme Court decisions are based primarily upon the ideological beliefs of the justices. The reason for this, they say, is that legal text is inherently indeterminate and that justices merely rationalize the legal outcomes they desire (referred to as “motivated reasoning.”) “Law,” therefore, does not constrain a justice when voting on the merits. In this work, I show that conservative justices do, in fact, defect significantly from political ideology in First Amendment cases involving “core” political speech. For this cherished American right, political attitudes as they are measured by empirical researchers do not dominate voting behavior. The reason for this, I contend, is that the a priori foundation of the attitudinal model is suspect. That is, there are occasions when justices regard legal text as sufficiently clear and when “principle” is more important than policy preference. When this happens, justices shun strictly ideological voting. Future works should identify other meaningful areas of Supreme Court decision making that are poorly explained by an ideological model.

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