Intra-party divisions and the electoral consequences of mainstream accommodation

When does mainstream accommodation of niche parties fail? Research demonstrates that mainstream parties rarely electorally benefit from adopting the positions of Eurosceptic and anti-immigration parties. Current explanations fail to explain why some mainstream parties fare better than others in comparable contexts. This paper highlights the key role of intra-party divisions in conditioning the success of accommodation. I posit that divisions constrain the ability of parties to credibly commit to policy shifts, alienating voters who demand them. Divided parties are also unable to convince voters who do not favor the changes. Consequently, they lose voters to niche and mainstream competitors. These propositions are supported by an analysis of issue competition on European integration in 51 national elections in 14 Western European countries from 2001 to 2021, combining voter and expert survey data. The findings highlight the key role of intra-party dynamics for electoral competition.