This project explores a general theory of membership growth and political position-taking by interest groups. The theoretical model represents the interaction of many individuals and interest groups in a large political landscape. The driving force in the model is the extent to which interest group entrepreneurs adapt to and interact with prospective members. The central research questions concern the evolution of an interest group system in which several groups may form and compete for members while attempting to accumulate resources with which to influence political outcomes. The groups compete with one another by altering their policy positions, the magnitude of their recruiting efforts and other attributes of the group. The model looks for patterns of stability while manipulating many of these parameters. The research uses a combination of formal models and computational modeling. A computer package called SWARM, developed at the Santa Fe Institute is used to conduct the simulations. These simulations are used to generate hypotheses about group positions and membership and how these affect when individuals will join and stay in interest groups.