Do anti-regime protests in electoral autocracies benefit the opposition by shifting the political preference of the bystanders? We seek an answer to this question by examining the electoral impact of Hong Kong's Umbrella Movement. Analyzing the election outcomes at the polling-station level shortly after the movement, we find that protest exposure, as measured by spatial proximity to protest sites, is positively correlated with the decline of electoral support for the opposition. Individual level surveys indicate that the adverse influences of protest exposure manifest themselves in elevating by-standing citizens' sense of economic insecurity, even though the movement causes no persistent income loss, while enhancing political efficacy.