We examine whether MPs and candidates for parliament are motivated by electoral self-interest, values, ideology, or all of these when evaluating proposals for changing electoral institutions. Using survey data from four countries (Australia, Germany, the Netherlands, and New Zealand), we find that candidates who won election are less supportive of proposals to change institutions, while those who lost elections are more supportive of institutional changes. Winning candidates share preferences for institutions that are independent of whether they are affiliated with a governing or opposition party. This self-interest effect is attenuated by ideology and attitudes about democracy. Pure self-interest, then, is an incomplete explanation for politicians’ attitudes towards electoral institutions. We discuss how these findings are related to the static nature of political institutions.