The Judean People’s Front vs. the People’s Front of Judea – Defections and Legislative Party Switching in New Political Parties

If a legislative party cannot retain its MPs between elections (they defect to switch parties or to form a new one whilst in parliament), it reveals that the routinisation of behaviour in that party was either never established or that it broke down. I propose to study legislative party switching as a sign of an incomplete party institutionalisation process (see also McMenamin & Gwiazda 2011). This is particularly important if the parties losing MPs are new, because it links party institutionalisation to party system institutionalisation: party system change is either stopped (new party MPs defect to older parties) or it is extended (defectors form even newer parties). What makes new parties vulnerable to defections? I consider a new party’s genetic model (the circumstances of their formation, Panebianco 1988), its party family, and whether it presents a new ideology or issue to the system. The rationale behind this is offered by new party literature (Bolleyer 2013 in particular): new parties presenting an ideology that is both new and attractive in the long run are more likely to be electorally successful, especially if they were helped by experienced politicians at conception. These characteristics should also make parties better equipped to institutionalise, but also to retain ambitious MPs, who are hypothesised to be motivated by votes, office or policy. A new dataset on defection and party switching has been compiled containing 129 new parties in 14 advanced democracies; analyses take place on party level and party-per-parliamentary-term level. As hypothesised, green parties are less likely to suffer defections. Interestingly, splinter parties are more likely to do so, suggesting that an incomplete party institutionalisation process is planted at formation. No consistent evidence was found supporting the hypothesis that votes, office and policy (measured at party level) are a necessary motive for switching MPs.