How does repression affect an emerging political movement? On the one hand, repression might stifle the movement’s mobilization efforts; on the other hand, repression might have a contrary effect by strengthening the coherence of the repressed. We study this question in the context of the socialist movement in late 19th and early 20th century Germany. In the first part of the paper, we use an original geo-coded dataset of more than 2,000 bans of socialist associations and publications based on the Socialist Laws (1878-1890) to analyze if the suppression of German Socialists triggered a regionally differentiated mobilization of the Social Democratic Party. Studying electoral outcomes at the electoral district level, we explore how the intensity of oppression is linked to the strength of the Social Democratic Party in the German Empire. We find that Social Democratic vote shares increased disproportionally in those districts where oppression was most intense. In a second step, we extend this analysis to the Weimar Republic to explore to what extent these differences persisted. Here, our results suggest a continued strengthening of the left, particularly of the more moderate left in regions that saw more intense oppression. On the other hand, repression is not correlated with stronger results for the Communist party, which could be expected if the repression had caused radicalization among the repressed.