Social mobilisation in partisan spaces

Three decades ago Huckfeldt and Sprague hypothesised that partisan context constrains infor- mation sharing between neighbours. We develop their theory to identify implications for campaign mobilisation in homogeneous and mixed-partisan contexts. We argue that GOTV spillover effects should vary with the proportion of rival party supporters in a neighbourhood. Based on two sam- ples of households that were either included or excluded pre-random assignment from a street-level GOTV experiment, we test this expectation of differential spillover effects. We estimate neigh- bourhood party preferences based on targeting data made available by the UK Labour Party. We find that spillover effects on party supporters are smaller in neighbourhoods that include larger shares of rival party supporters. Rival partisans are mobilised in mixed partisan neighbourhoods where the probability of spillovers from mixed partisan households is higher. This paper extends Huckfeldt and Sprague’s theory, and demonstrates the importance of social dynamics for parties’ campaign strategies.