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The politics of economic self-interest that underpinned the New Deal era have been supplanted by “expressive partisanship,” a form of “affective polarization,” as political scientists put it.

What does this mean?

“A distinctly social type of polarization that includes political prejudice, anger, enthusiasm, and activism” has superseded political conflict over issues, Lilliana Mason of the University of Maryland, argues in her new book, “Uncivil Agreement”:

An electorate that increasingly treats its political opponents as enemies, with ever-growing levels of prejudice, offensive action, and anger, is a clear sign of partisan polarization occurring within the citizenry. If issue positions do not follow precisely this pattern of behavioral polarization, it does not make those increasingly tribal partisan interactions irrelevant.

Mason elaborated in an email: “The more highly educated also tend to be more strongly identified along political lines.” And the depth of their education plays a role:

Political knowledge tends to increase the effects of identity as more knowledgeable people have more informational ammunition to counter argue any stories they don’t like.

In a 2016 study, the Pew Research Center found that not only are American voters developing increasingly consistent conservative or liberal positions, but that

Much of the growth in ideological consistency has come among better educated adults — including a striking rise in the share who have across-the-board liberal views, which is consistent with the growing share of postgraduates who identify with or lean toward the Democratic Party.

In “Uncivil Agreement,” Mason contends that “an increasing portion of the American electorate is driven by identity-centric motivations.” And she explains it, “We are acting because our emotions and the self-esteem that is driven by our identities compel us to do something.”

The attitudes and beliefs of individual voters

cannot compel the same sort of activism that our simple sense of social connection can. We take political action, potentially making real political changes, because we feel close to particular groups of people and want them (and therefore ourselves) to be winners.

In this view, the strength of a voter’s identity as a Democrat or Republican drives political engagement more than personal gain. Better educated voters more readily form “identity centric” political commitments to their party of choice, which goes a long way toward explaining the strength of liberal convictions among more affluent Democrats.

In a recent paper, “Education is Related to Greater Ideological Prejudice,” P.J. Henry and Jaime L. Napier, psychology professors at NYU-Abu Dhabi, argue that we are exchanging one type of bias for another — that while “education is related to decreases in interethnic/interracial prejudice,” it simultaneously leads “to increases in ideological — liberal vs. conservative — prejudice.”