A wealth of research documents the rise of affective polarization, or the increasing disdain for the out-party in American politics. In this paper, we analyze ANES data from 1988 to 2016 to investigate the contribution of core value polarization to the phenomenon of out-party enmity. We find that greater differences in fundamental principles relate significantly to emotionally intense evaluations of the opposing party and its candidates, as well as the ideological out-group, independent of issue attitude extremity and the strength of one's partisan and ideological identities. Moreover, ANES panel data from 1992 to 1996 reveal that past value extremity promotes future affective polarization. These results are important for our understanding of the nature and extent of value-based polarization in American politics.