Do local political institutions influence the balance of power in national politics? If so, how? Drawing on insights from the literatures on multi-level politics, party organization and strategy, and the effects of institutions, I argue that certain local political institutions strengthen party branches. This, in turn, leads to better performance in national elections, particularly for parties that rely on grassroots mobilization. To test the argument, I take advantage of a quasi-experimental local governance setup in early-20th-century Sweden. I find that municipalities with elections show markedly different support for major parties in national elections compared to municipalities that use traditional community meetings. In accordance with the theory, parties relying on grassroots mobilization receive greater support in places with elections. Furthermore, this pattern is stronger in places with a robust local-activist presence. My results demonstrate that local-level institutions significantly impact national politics, with consequences for institutional reform outcomes and citizen welfare.