In his most recent New York magazine column, Andrew Sullivan reviews two new books on the same issues from different perspectives: Ezra Klein’s Why We’re Polarized and Christopher Caldwell’s The Age of Entitlement.

… both books agree on one central thing: Our fate was almost certainly cast as long ago as 1964 and 1965. Those years, in the wake of the Kennedy assassination, saw the Civil Rights Act upend the Constitution of a uniquely liberal country in order to tackle the legacy of slavery and racism, and the Immigration and Nationality Act set in motion the creation of a far more racially and ethnically diverse and integrated society than anyone in human history had previously thought possible. Still, at the time, few believed that either shift would have huge, deep consequences in the long term. They were merely a modernization of American ideals: inclusivity, expansiveness, hope.

As someone who was born just before these two changes were instigated, I regarded those tectonic shifts as simply part of the landscape — something that seemed always to have been here. And what could be questioned about either? One was reversing a profound moral evil; the other was banishing racism from the immigration laws. No-brainers. The strongest resistance to civil rights came from former segregationists or obvious racists, and there was little resistance to the Immigration Act, because most in the congressional debate seemed to think it wouldn’t change anything much at all. (The House sponsor of the Immigration Act, as Caldwell notes, promised that “quota immigration under the bill is likely to be more than 80 percent European,” while Ted Kennedy insisted: “The ethnic mix of this country will not be upset.”) There were a few dissenters to the 1964 Act, such as Robert Bork, who identified a significant erosion in the freedom of association. And there were southern senators who worried about immigrants from the developing world. But the resisters were easily dismissed on both counts, in the wake of LBJ’s 1964 landslide.

In fact, as Klein shows, a pivotal moment had arrived. The civil-rights movement quickly broke apart the old Democratic party, which had for decades combined the interests of blacks and southern whites into a single multiracial coalition. The result was a sorting of the two political parties into much purer vessels for their diverging ideologies, and into groupings that were also increasingly racially distinct. The GOP became whiter and whiter; the Democrats more and more became the party of the marginalized nonwhites as the years rolled by. Blacks and southern whites ceased to communicate directly within a single party, where compromises could be hammered out through internal wrangling. In the aggregate this was, as Klein emphasizes, a good thing — because blacks kept coming out the losers in those intraparty conversations, and with civil rights, they had a chance of winning in a clearer, less rigged, debate.

But it was also problematic because human beings are tribal, psychologically primed to recognize in-group and out-group before the frontal cortex gets a look-in. And so the whiter the GOP became, the whiter it got, and the more diverse the Democrats got. Simultaneously, the economy took a brutal toll on the very whites who were alienated by the culture’s shift toward racial equality, and then racial equity. Klein recognizes that this racial polarization, is, objectively, a problem for liberal democracy: “Our brains reflect deep evolutionary time, while our lives, for better and worse, are lived right now, in this moment.” So he can see the depth of the problem of tribalism — and its merging with partisanship, which goes on to create a megatribalism.

If humans simply cannot help their tribal instincts, then a truly multicultural democracy has a big challenge ahead of it. The emotions triggered are so primal, that conflict, rather than any form of common ground, can spiral into a grinding cold civil war. And you can’t legislate or educate this away. One fascinating study Klein quotes found that “priming white college students to think about the concept of white privilege led them to express more racial resentment in subsequent surveys.” Anti-racist indoctrination actually feeds racism. So tribalism deepens.

Klein sees this spiral more clearly than most on the left. He acknowledges the truth that in a period of extraordinary demographic and racial change — the U.S. is the first majority-white nation that will become majority nonwhite in human history — every group begins to feel like an oppressed minority. Including whites: “To the extent that it’s true that a loss of privilege feels like oppression, that feeling needs to be taken seriously, both because it’s real, and because, left to fester, it can be weaponized by demagogues and reactionaries.” And the truth is: It was left to fester. Whenever whites resisted ever-expanding concepts of civil rights or mass illegal and legal immigration, they were cast outside the arena of permissible disagreement, deemed racists, and stigmatized. Even the GOP scorned them. Eventually, Hillary Clinton named them: the deplorables. By 2016, plenty of Americans decided to embrace the label, and voted for Trump.