ABSTRACT
This chapter reconstructs the determinants of party switching. The simplest way to explain parliamentarians’ decisions to switch parliamentary groups, based on the vote-, office-, and policy-seeking model, is questioned, as it does not satisfactorily account for this type of behaviour. The chapter’s contribution is a proposal to include reputations of MPs and their parliamentary groups, as well as emotions related to affective polarisation, in the set of determinants. Regarding systemic determinants, the chapter highlights inconclusive results from research on the impact of party cohesion on the likelihood of party switching. The topic of situational variables affecting the dynamics of parliamentary volatility is also addressed. It is pointed out that political regimes of presidentialism and parliamentarism do not directly impact party switching but nevertheless influence its nature. In the context of electoral systems, the lack of significant empirical evidence on the relationship between them and party switching may be attributed to the classification adopted. Arguments are presented for the thesis that the division of electoral systems into party-centred and candidate-oriented works better in the study of volatility. The chapter also discusses legal determinants of party switching, including anti-defection procedures and thresholds for the formation of parliamentary groups.
