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

Abstract: 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.

• Conference paper: download Word version.