Students of social movements for a long time have struggled with the question how relatively abstract political opportunities, such as elite division, reveal themselves to activists. Building on Tilly’s ideas about state movement interactions the authors argue that the relationship between institutional opportunities and decisions to mobilize takes the form of trickle-down politics. In this view activists learn about political opportunities indirectly through the changes that political developments bring about in the immediate social setting in which they protest. In particular they investigate how bystander responses transmit information about the wider political context to unorganized extreme right activists without much knowledge of national politics. Time-series analysis, event history models and illustrative cases indeed indicate that temporalspatio-temporal fluctuations in political opportunities and public sentiments are translated into mobilization after activists receive feedback from local bystanders. This suggests that bystander responses, a research topic that has only received scant scholarly attention, play a crucial role in the perception of political opportunities.
