Social mobilization in partisan spaces

Three decades ago Huckfeldt and Sprague hypothesized that partisan context constrains information sharing between neighbors. We develop their theory to identify implications for campaign mobilization in homogeneous and mixed-partisan contexts. We argue that get-out-the-vote (GOTV) spillover effects should vary with the proportion of rival party supporters in a neighborhood. Using two samples of households that were either included or excluded prerandom assignment from a street-level GOTV experiment, we test this expectation of differential spillover effects. We estimate neighborhood party preferences using targeting data made available by the UK Labour Party. We find that spillover effects on party supporters are smaller in neighborhoods that include larger shares of rival party supporters. Rival partisans are mobilized in mixed-partisan neighborhoods where the probability of spillovers from mixed-partisan households is higher. This article extends Huckfeldt and Sprague’s theory and demonstrates the importance of social dynamics for parties’ campaign strategies.