A Downsian Spatial Model with Party Activism

Abstract

A unidimensional spatial model is proposed in this article. Although its formal structure parallels the spatial model of electoral competition, this model examines the decisions of individuals as they choose whether or not to become activists in one of two political parties. An individual “calculus of participation” is developed that is similar to the spatial interpretation of the “calculus of voting.” This calculus is then generalized by examining conditions that may hold for aggregate activism probabilities, and the relationship between the two forms is investigated. Some results are then presented which concern the distributions of activists in the two parties. These results in general conform to the existence of “party cleavages,” in which there are two stable (equilibrium) distributions of activists, such that the two parties' activists are relatively cohesive internally and relatively distinctive externally. Finally, some suggestions are offered about how this model can be combined with the spatial model of candidate competition to provide a more complete model of elections.