Abstract
When does success in one social movement catalyze mobilization in another? On the one hand, resource mobilization theory predicts that the growth of one movement crowds out the mobilization of others, while research on social movement spillovers suggest that learning mechanisms enable movements to build on the success of one another. However, both accounts emphasize those who are already involved in social movement activism. Exposure to social movement mobilization activity also affects dormant populations—those who have not engaged in activism due to their lack of belief in the power of social movement tactics to initiate a desired change. We show that the susceptibility of a region to the spread of social movements depends on the region's tactic efficacy beliefs--shared attitudes about the effectiveness of social movement tactics. Using 1.6 million posts from 29,000 users on the largest online forum for ride-sharing drivers, we show that counterintuitively, regions with strong tactic efficacy beliefs reduce ride-share mobilization in response to exposure to other movements. By contrast, efforts to organize in regions with weaker tactic efficacy beliefs are more likely to result in protest activity growth. In addition, we employ a shift-share instrument (SSIV) to estimate the causal impact of social movement mobilization exposure on real-world labor movement mobilization activity based on 2.6 million news stories across 14 social movements. Our conceptualization of tactic efficacy beliefs contributes by developing a novel explanation for the spread of social movements.