Since the 2016 elections and the UK's Brexit vote, "populism" has become an ambiguous word, inspiring approval but also fear. How well do we even understand it? As Lawrence Rosenthal defines it, right-wing populism is an ideologically flexible force driven by resentment toward immigrants, minorities, and cultural elites. In America and abroad, the current mobilization of populism has given life to long marginalized threats like white supremacist groups. Painting a vivid political and psychological picture of international populism, Rosenthal argues that the future of democratic politics in the United States and abroad depends on whether leftist parties can mount a progressive agenda of their own.