It is often taken for granted that parties support electoral reform because they anticipate seat payoffs from the psychological and mechanical effects of the new electoral system. Although some studies point out that elements related to values and the willingness to achieve social goals are also relevant to explaining party preference in those situations, a general model of how these considerations influence support for electoral reform is still missing. To fill this gap, I develop in this article a policy-seeking model accounting for values-related factors and operationalize it using one of the most firmly established effects of electoral systems in the literature: The degree of inclusiveness and its consequences for the representation of social groups in parliament. The empirical relevance of this model is then tested using an original dataset reporting the actual position of 115 parties facing 22 electoral reform proposals in OECD countries since 1961. The results show that willingness to favour the electoral system most in line with a party’s electoral platform has a unique explanatory power over party support for a more proportional electoral system. In turn, values appear to be as crucial as party self-interest in explaining the overall electoral reform story.