Anti-defection rules and party switching in the Italian Parliament

Despite considerable progress in the study of party switching, scholarly interest in institutional constraints explicitly designed to limit or penalise inter-party mobility remains limited in the literature. This paper contributes to the emerging scholarship on party switching and legal institutional constrains by assessing the effectiveness of the new anti-defection regulations introduced in the Italian Senate starting from 2018. To evaluate the impact of this intervention, we develop two quasi-experimental research approaches that take advantage of the bicameral structure of the Italian Parliament and the fact that the anti-defection regulations were only implemented in the Senate and not in the Chamber of Deputies. Our results indicate that anti-defection regulations failed both to limit inter-party mobility and the formation of new legislative parties. However, they results effective in influencing the timing of party switching, concentrating it in the phases of government formation and dissolution.