Civic associations are often expected to foster civic, pro-social behavior, but this optimistic view is increasingly contested. The political context is crucial for understanding the effects of associations. We argue that populist radical right parties can strategically target and infiltrate civic associations in order to diffuse their anti-establishment rhetoric, spreading anti-democratic attitudes and norms. We illustrate this phenomenon by examining the relationship between civic associations and compliance with government rules during the first Covid lockdown of 2020 in Germany with a difference-in-differences design. Results show that areas with denser sport, nature, and culture clubs recorded higher mobility under lockdown restrictions. To document the infiltration mechanism and the spreading of anti-democratic attitudes within associations, we use survey and election data and qualitative evidence including interviews. In doing so, we shed light on a negative effect of social networks and on an understudied strategy of challenger populist parties.