Replication Data for: Contagion from abroad. How party entry in Western Europe is influenced by party family members abroad, 1961-2016

New parties are a key mechanism behind party system innovation as voters are offered new choices. To explain party entry (i.e., participation in a lower house election for the first time), the state-of-the-art has typically focused on domestic determinants. This, however, assumes that party entry takes place in an international vacuum. Building on the policy diffusion literature, we explore how party family members abroad influence party entry in the focal country. Based on a new dataset on the evolution of each party family in 17 Western European party systems between 1961 and 2016, including 2191 new parties, our mixed-methods approach combining spatial econometric models with pathway case analysis demonstrates that party entry is influenced by the entry and electoral success of their party family abroad. This has important implications for the literature on party entry and the international diffusion of policy platforms.