How does political polarization affect the welfare of the electorate? We analyze this question using a framework in which two policy and office motivated parties compete in an infinite sequence of elections. We propose two novel measures to describe the degree of conflict among agents:antagonismis the disagreement between parties;extremismis the disagreement between each party and the representative voter. These two measures do not coincide when parties care about multiple issues. We show that forward-looking parties have an incentive to implement policies favored by the representative voter, in an attempt to constrain future challengers. This incentive grows as antagonism increases. On the other hand, extremism decreases the electorate’s welfare. We discuss the methodological and empirical implications for the existing measures of political actors’ ideal points and for the debate on elite polarization.