Party positions and the seats/votes relationship with ideological voters

Abstract

Chapter 2 is based on two axioms: party members must run under common platforms, but are made up of incumbents who seek their own individual re-election. Politicians seek to win their own seats in the legislature, but they must run under a common party label. In both single-member district and proportional representation systems, equilibrium platforms are shown to diverge substantially, with one party located near the 25th percentile of the voter distribution and the other near the 75th percentile, rather than converge to the median. The model also yields predictions concerning short-term economic shocks, incumbency advantages, and gerrymandering. Chapter 3 is based on ideological voters. With purely ideological voters, party vote share depends on the distribution of voters in the entire country. Seat share depends on distribution of district medians. The seats/votes curve is therefore a combination of two different functions. This presents an identification problem for studying either function without accounting for the other. The incumbency advantage is also considered. Chapter 4 measures ideology using the Cooperative Congressional Election Study using factor analysis on voter responses to policy questions. I discuss the robustness of the measure and implications for the model of chapter 3. Chapter 5 finds little evidence of structural bias against either party under districting. However, in a hypothetical party-list system, there would be a massive structural advantage for the left party. The seats/votes curve is predicted to be approximately linear or logistic, unless one takes into account incumbency, in which case the curve becomes non-linear. Senate party platforms are predicted to be more converged than the House, with a midpoint right of center.