Estimating the effects of activists in two-party and multi-party systems: comparing the United States and Israel

This article presents an electoral model where activist groups contribute resources to their favored parties. These resources are then used by the party candidates to enhance the electoral perception of their quality or valence. We construct an empirical model of the United States presidential election of 2008 and employ the electoral perception of the character traits of the two candidates. We use a simulation technique to determine the local Nash equilibrium, under vote share maximization, of this model. The result shows that the unique vote-maximizing equilibrium is one where the two candidates adopt convergent positions, close to the electoral center. This result conflicts with the estimated positions of the candidates in opposed quadrants of the policy space. The difference between estimated positions and equilibrium positions allows us to estimate the influence of activist groups on the candidates. We compare this estimation with that of Israel for the election of 1996, and show that vote maximization leads low valence parties to position themselves far from the electoral origin. We argue that these low valence parties in Israel will be dependent on support of radical activist groups, resulting in a degree of political fragmentation.