Electoral Rules and the Emergence of New Issue Dimensions

Different electoral rules provide different incentives for parties competing for votes to adopt emerging issues. As a result, new societal issues will be integrated at different speeds into the political arena, and ultimately, into policy. In order to study this question formally, I propose an extension of the standard spatial model of political competition that allows for issue adoption and more generally, issue prioritizing at the platform level. The paper then compares the outcome of party competition under proportional and plurality rule. Entry is allowed and incumbent parties act as Stackelberg leaders vis-à-vis potential entrants. The analysis highlights the interaction between entry barriers and the type of emerging issue in determining when and how a new issue will be introduced. The theory explains both internal (that is, without entry by a new party) realignments of party systems along new dimensions and entry as part of the process of political realignment.