Social movements strive for social change that realizes their ideal of how the ‘perfect world’ should look like. Movements want to succeed as fast as possible and therefore try to find the most effective ways of influencing decision-makers. In parliamentarian democracies, the central decision-makers are political parties. Much of the existing literature emphasizes the use of public pressure and lobbying. In contrast, I argue that personal overlap between political parties and social movements is the strongest and most stable way for activists to influence politicians. Using novel micro data on the German antinuclear movement, and in particular its success in influencing the shutdown of nuclear power plants, I show how movements realize their goals significantly faster when they increase their personal overlap with political parties. My results suggest that there is a tipping-point of the effect of personal overlap if more than 30 percent of Greens in parliament are antinuclear activists. Beyond the tipping point, influence declines.
