On Measuring Partisanship in Roll Call Voting: The U.S. House of Representatives, 1877-1999

Abstract

We propose a method of assessing party influence, based on a spatial model. Our method provides the first test of whether observed values of the widely used Rice index of party dissimilarity are consistent with a "partyless" null model. It also avoids problems that beset previous estimators. Substantively, we find evidence of party influence in all but one Congress since 1877. Moreover, our indicator of party pressure is systematically higher for the sorts of roll calls that party theorists believe are more pressured-procedural, organizational and label-defining votes. Our results refute the widespread notion that parties in the House have typically had negligible influence on roll call voting behavior. They also document important changes in party influence associated with the packing of the Rules Committee in 1961 and the procedural reforms of 1973.