U.S. politics increasingly looks like a savage battle between left and right. Consistent with closing ranks in a battle, Americans are expressing policy opinions that align more and more with their political groups. Of all conflicts between groups in America, partisanship is one of the most divisive, with 86% of Americans seeing strong conflicts between Republicans and Democrats. Yet, political differences are not always caused for alarm. Increased sorting could reflect identification with groups that better match our values. Perhaps Republicans and Democrats can’t compromise because their policy preferences are irreconcilable. However, this doesn’t explain why Americans personally dislike political opponents with such intense fervor.
U.S. liberals and conservatives not only disagree on policy issues: they are also increasingly unwilling to live near each other, be friends, or get married to members of the other group. This rejection based on group membership is called affective polarization, meaning that our feelings (affect) are different towards members of our own group compared to outsiders. Growing intolerance in the U.S. is a puzzle because disagreeing about policies need not cause rampant mistrust and legislative gridlock. For example, countries with proportional electoral representation like Germany create functional coalitions across different ideologies.