How do parties react to defections? Electoral strategies after a valence loss

Switches produce a lack of credibility and damage a party's image, signalling weakness and an inability to select loyal MPs and preserve unity. Accordingly, we consider party out-switching as a valence loss for the party. By combining information on party manifestos with a novel database on 2053 episodes of party switching, we investigate which electoral strategies parties adopt to reduce the negative consequences of such valence loss. Analyzing 1,131 manifestos related to 135 parties in 14 Western European democracies, from 1945 to 2015, we show that parties try to restore their positive image by investing on valence, in terms of competence, clarity and core issues. An instrumental variable approach corroborates our results. The findings have implications for spatial modelling, valence politics, issue ownership and issue competition.