We consider a class of dynamic collective action problems in which either a single principal or two competing principals vie for the support of members of a group. We focus on the dynamic problem that emerges when agents negotiate and commit their support to principals sequentially. We show that competition reduces agents' welfare with public goods, or if and only if there are positive externalities on uncommitted agents, and increases agents' welfare with public bads. We apply the model to the study of corporate takeovers, vote buying, and exclusive deals.

We estimate an equilibrium model of decision making in the US Supreme Court that takes into account both private information and ideological differences between justices. We measure the value of information in the court by the probability that a justice votes differently from how she would have voted without case-specific information. Our results suggest a sizable value of information: in 44 percent of cases, justices' initial leanings are changed by their personal assessments of the case. Our results also confirm the increased politicization of the Supreme Court in the last quarter century. Counterfactual simulations provide implications for institutional design.