How Party Switches Affect the Clarity of Party Labels and Electoral Manifestos

What are the effects of party divisions on the clarity of party labels and on the content of electoral manifestos? Focusing on party switching, and using an original dataset on inter-party changes, we investigate how parliamentary defections affect the policy proposals of parties hit by switches. Under the idea that the policy preferences of out-switching parties should become more homogenous after witnessing defections, we hypothesize that high levels of switching should enhance the clarity of party labels and reduce the ambiguity of policy proposals. This effect, though, can be moderated by institutional constraints, such as parties’ internal rules and the shape of intra-party decision-making. The model of a party (niche or mainstream), its ideology, and the government/opposition divide can also play a role. Our hypotheses are tested by means of statistical analysis, using recent data on the ambiguity of electoral manifestos. Our analysis includes 296 observations related to 80 parties from 11 West European countries in 49 elections, starting from 1980. The results have implications for the literature on legislatures, intra-party politics, party shifts and policy change.