For decades, political scientist Sidney Tarrow has been a leading expert on social movements, political parties, and, more broadly, the strategies and dynamics of political contention. As a Clough Distinguished Lecturer, Tarrow will draw on his extensive comparative research into European democratic regimes to speak to the challenges polarization poses to American democracy today. He will also make the case that the postwar experience of European countries can afford valuable insights into the nature of these challenges, and how they might be addressed. Tarrow’s respondent will be Marshall Ganz, the Rita E. Hauser Senior Lecturer in Leadership, Organizing and Civil Society at Harvard Kennedy School, and one of the foremost scholars and practitioners of community organizing.