Sadiraj, V., Tuinstra, J. and van Winden, F.A.A.M. (2006). A computational electoral competition model with social clustering and endogenous interest groups as information brokers Public Choice, 129(1-2):169--187.

We extend the basic model of spatial competition in two directions. First, political parties and voters do not have complete information but behave adaptively. Political parties use polls to search for policy platforms that maximize the probability of winning an election and the voting decision of voters is influenced by social interaction. Second, we allow for the emergence of interest groups. These interest groups transmit information about voter preferences to the political parties, and they coordinate voting behavior. We use simulation methods to investigate the convergence properties of this model. We find that the introduction of social dynamics and interest groups increases the separation between parties platforms, prohibits convergence to the center of the distribution of voter preferences, and increases the size of the winning set. A previous version of this paper, entitled 'Interest Groups and Social Dynamics in a Model of Spatial Competition', was presented at the Public Choice Society meetings, March 2000, Charleston, South Carolina, U.S., at the 7th Viennese Workshop on Optimal Control, Nonlinear Dynamics and Dynamic Games, May 2000, Vienna, Austria and at the Computational Economics Conference, July, 2000, Barcelona, Spain. Comments by Arno Riedl and Randolph Sloof are gratefully acknowledged.