New political parties are an important source of change in the party systems of modern democracies, but these parties often struggle to gain and retain parliamentary representation. This article addresses the question of which of the parties that were successful in European Parliament elections also enter national parliaments, and why. FsQCA analysis show that a combination of experienced leadership, membership in a European Parliament political group and an electoral system without high barriers for new entrants explains most cases of parties that are successful in entering the parliament at the national level. It does not, however, explain why others are not successful, indicating that the causation is asymmetrical.