The use of referendums has increased both on the national and sub-national level in the last three decades. Direct democracy was described by previous scholars as a panacea for increasing disenchantment with politics and politicians. Political parties experiment with intra-party referendums to open the internal decision-making process. Although such elements of direct democracy were often criticized for reinforcing leadership dominance within the parties, they allow members access to the decision-making process. This paper aims to explain why some political parties in Europe adopt and use intra-party referendums, while others do not. It focuses on the parliamentary parties in the EU member states plus Iceland, Norway and the UK between 2010 and 2023. Our explanatory framework focuses on party-level characteristics such as formation, ideology, age, size, factionalism, electoral performance, and complexity of party organization.
