Conditional Party Government and the Homogeneity of Constituent Interests

Abstract

The conditional party government (CPG) theory posits that political parties will be strong when they are polarized and homogeneous. The homogeneity of the parties is generated from the homogeneity of constituent coalitions. However, these root causes of constituent interests have remained largely untested. By focusing on trade policy issues, we can provide one such test, albeit limited, because the level of factor mobility a priori defines constituent interests and the relative homogeneity of constituent coalitions. Using ideal point estimation and an originally compiled data set of constituent economic demographics at the level of U.S. House districts from 1963 to 1992, I confirm the constituent foundations of the conditional party government theory for trade policy and add factor mobility to the secular trends that have contributed to the decline and resurgence of American political parties.