This Doctoral Dissertation Research Support investigation examines the process of representation in American legislatures by focusing on the effect of political party system upon legislator roll call decisions. Poole and Rosenthal (1997) found that most roll call vote can be explained by a simple one or two dimensional model, in which the primary dimension is political ideology. However, recent work suggests that this low-dimensional structure tends to break down when two-party electoral competition declines.
This dissertation explores this apparent linkage between party system and the level of structure found in roll call votes by looking at three state legislative chambers. Each chamber is characterized by a different party system. Roll call data collected from these three states permits the evaluation of hypotheses regarding the impact of party electoral competition on the dimensionality of roll call voting and the distribution of member ideal points along those dimensions.
