The theory of the book emphasizes the radical right’s reactive nature and implies that the success of ethnic and socially liberal parties contributes to explaining temporal variation in voting for radical right parties. Chapter 3 uses an original time-series cross-national dataset covering all post-communist democratic elections after 1989 to assess the project’s core propositions about the electoral success of radical right parties at the cross-national level and over time. The results show that radical right parties tend to be more successful when ethnic and socially liberal parties (1) obtain policy-making powers via coalition participation, (2) express greater ideological extremism and (3) win a greater proportion of the popular vote. The chapter also discusses the modifying effect of ethnic group size and shows that the existence of an ethnic minority facilitates radical right mobilization but that mobilization is not proportional to minority group size.