Disaggregating Party Strategies inTwo-Party Systems: A Theory and the Case of the United States.

This paper addresses the question of how national party leaders set their party’s policy positions. Currently, the literature on this question exhibits a gap between theory and reality; spatial models predict convergence of party policy positions in a two-party setting, while empirical scholars found divergence in real world situations. Our paper is an attempt to fill in this gap. We do so by introducing two additional issues that have been relatively neglected in the existing literature. First, we stress the importance of establishing a party label for national party leaders as part of a strategy for the goal of seat-maximization in addition to the Downsian convergence strategy. Second, we address the issue that national party leaders are likely to adjust their party policy positions in response to heterogeneous preference distributions of voters across districts, in which the party has varying degrees of success. Incorporating these two issues, we show in a simple spatial model that in a two-party, single-member plurality system, two parties’ positions on a given policy issue are likely to converge if the given policy issue is at stake in closely competed districts, while two parties’ positions on a given policy issue are likely to diverge if the given issue is at stake in districts where one of the parties already has a secure majority. We use the case of the US party system (1945-2000) as the empirical test and find that the regression results are consistent with this hypothesis. [ABSTRACT FROM AUTHOR]