While previously polarization was primarily seen only in issue-based terms, a new type of
division has emerged in the mass public in recent years: Ordinary Americans increasingly
dislike and distrust those from the other party. Democrats and Republicans both say that the
other party's members are hypocritical, selfish, and closed-minded, and they are unwilling to
socialize across party lines. This phenomenon of animosity between the parties is known as
affective polarization. We trace its origins to the power of partisanship as a social identity …