Much has been written about politicians’ preferences for electoral systems, yet little is known about the preferences of citizens, who ultimately legitimize them with their ballots. We use the 1993 binding electoral referendum in New Zealand in order to find out what drives citizens’ preferences for an electoral system. The referendum asked voters to choose between a single plurality system (First Past the Post) and a pure proportional one (Mixed Member Proportional). We construct a new dataset merging results from all nationwide polling stations, and benefit from the fact that a general election was held the very same day. We find that strategic self-interest was a key driver: voters preferred the system that most benefited their favorite party. Furthermore, despite the absence of malapportionment, we find that rural voters strongly preferred a plurality system. The data set allows us to recover preference intensities: individuals in rural areas, supporters of National (the conservative party), and Maori seemed to have had more at stake. Using post-electoral survey data from 1993, we can further show that liberal values also shape citizens’ preferences over and above partisan self-interest: people who held more progressive values were more likely to support a proportional system. Finally, we find that men, more educated citizens and religious minorities were more supportive of a proportional system. We provide a framework to rationalize these findings.