How intra-party divisions affect mainstream party strategies on niche party issues

How do intra-party divisions affect mainstream party salience and spatial strategies on niche party issues? Even though niche parties purposefully seek out competition on issues that internally divide mainstream parties, previous explanations have mostly sidelined the role of intra-party divisions as a key driver of mainstream party strategy selection. I argue that mainstream parties are incentivized to downplay internally contentious niche party issues to avoid putting a spotlight on their divisions. However, divisions may pressure parties into changing their positions on the issue. Testing the theoretical argument on the issue of European integration using expert data on over 75 mainstream parties in 14 Western European democracies between 1984 and 2019, I find that mainstream parties deemphasize internally divisive issues and undergo stronger position changes on these issues than internally united parties. The findings contribute to our understanding of parties as non-unitary actors, highlighting the vital role of intra-party dynamics for party competition, and exposing the conflicting logics of mainstream party strategizing. While party leaders may generally favor vote-seeking strategies, divisions force them to prioritize internal cohesion.