Opposition backlash and platform convergence in a spatial voting model with campaign contributions

This paper investigates the effects of campaign contributions on candidate behavior in elections. The particular focus is on how candidates choose their platforms when they know that the positions they take will influence the level of campaign contributions that they (and their opponents) receive from concerned interest groups. The analysis is carried out in the context of a simple one- dimensional spatial voting model with two candidates and two interest groups. Since the earliest Hotelling-Downs formulations, a central issue in the literature on spatial voting has been the degree to which, under various sets of assumptions, the candidates' platforms converge in equilibrium. This paper extends that literature by examining how the introduction of interest groups making campaign contributions affects the degree of platform convergence. The paper shows that when choosing their platforms, candidates face a trade-off between generataing increased support from opponents and provoking a backlash from the opposition. An example is developed to illustrate a surprising result that can occur because of the backlash effect: the introduction of two extremist interest groups may lead the candidates to moderate their platforms, resulting in a greater degree of platform convergence than would be observed in the absence of any campaign contributions.