  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 ageing. Policy process theory maintains that learning
within and across coalitions is a central predictor of coalition formation and
policy change but has yet to explain how policy learning works. The present
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 to the debate. Belief adoption
matters in three complementary ways: bonding, which exploits cues within
coalitions; bridging, which explores new beliefs outside one's perimeter in the
debate; 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 dataset
using statistical network analysis and event history analysis.
