Candidate effects and spill-over in mixed systems: Evidence from New Zealand

Although mixed member proportional (MMP) systems offer several advantages they also have one potential problem that threatens the legitimacy of electoral outcomes. Some suggest that these systems suffer from a ’contamination effect’ where candidates have the potential to influence the party list vote which ultimately determines the partisan composition of parliament. This paper examines this theory in New Zealand which has conducted four elections under MMP. The analysis is based on district level data merged with individual level data. The findings suggest that although many voters do not have an opinion of candidates, those who do are likely to evaluate incumbents and party leaders more positively. While these factors can also have an influence on the party list vote, the overall effect is quite limited.