Social movement theory has rarely been tested with counterfactual cases, that is, instances in which movements do not emerge. Moreover, contemporary theories about political opportunity and resources often inadequately address the issue of motivation. To address these shortcomings, this article examines 20 communities that are at risk for mobilization because they face controversial proposals for large energy infrastructure projects. Movements emerge in only 10 cases, allowing for the identification of factors that drive mobilization or nonmobilization. Utilizing insights from social psychology, the authors contend that community context shapes motivations to oppose or accept a proposal, not objective measures of threat. They conclude that the combination of community contextto understand motivationand measures of capability is the best way to model movement emergence.