Electoral regimes and party-switching

This article presents an inquiry into the causes of party-switching under two different electoral regimes. It exploits a natural experiment in South Africa, where a large number of local legislatures are elected using the same mixed system, to examine how the party-switching behaviours of legislators elected under proportional representation (PR) rules may differ systematically from those of legislators elected from single-member districts. It confirms the findings of other single-legislature studies in concluding that PR legislators are more likely, ceteris paribus, to defect. It highlights several characteristics of legislative bodies and legislative districts that influence defection rates for legislators in South Africa. In so doing, it uncovers evidence that, despite the young age of South Africa’s post-1994 party system, the unexpectedly large volume of party-switching that occurred there was neither a simple party realignment nor an opportunistic scramble, but rather a highly organized, structured and strategic market for parties.