Time and again, changes to the electoral system have been driven by the vested interests of political players primarily interested in maximizing their gains, measured by the number of seats filled in parliament. History knows many cases in which such reforms were counterpro-ductive and destabilized the functioning of the political system. This raises the question of whether it is possible to reform the electoral system in a way that not only does not result in a chaotic shift in the balance of power on the political scene but, above all, serves to improve the functioning of democratic institutions. This article discusses the implications for the party system of the 1993 reform of New Zealand’s electoral law for the House of Representatives, involving a departure after 138 years from a plurality system to a mixed-member proportion-al system (MMP). The New Zealand case demonstrates that even a revolutionary change in the electoral system does not necessarily lead to a profound and disorderly remodeling of the party system, with the side effect of disrupting the functioning of the whole political system.