Endogenous coalition formation in policy debates

Abstract Political actors form coalitions around their joint normative beliefs in order to influence the policy process on contentious issues such as climate change or population aging. Policy process theory maintains that learning within and across coalitions is a central predictor of policy change but has yet to explain how policy learning works. This article explains the formation and maintenance of coalitions by focusing on the ways actors adopt policy beliefs from other actors in policy debates. A policy debate is a complex social system in which temporal network dependence guides how actors contribute ideological statements. Belief adoption matters in three complementary ways: bonding , which exploits cues within coalitions; bridging , which explores new beliefs outside one's perimeter; and repulsion , which reinforces polarization between coalitions and cements their belief systems. We formalize this theory of endogenous coalition formation in policy debates and test it on a micro‐level empirical data set.