Democrats can’t be content-of-character liberals anymore. They can’t hold to the liberal premise of individual rights, not when group identity has become the first determination of who and what a person is.

The sorry descent of former Vice President Joe Biden into identity politics on the campaign trail signals that the Democratic Party of Tip O’Neill and Bill Clinton is over and done with forever. The pull of group resentments in the party is too strong. Last summer, Biden staked his place in political correctness, and he hasn’t let up since then.

When Senator Kamala Harris (D-Calif.) charged Biden with flirting with racism in his rejection of busing many decades ago, a clear line was there for him to draw. Would Biden fall on the defensive and back off on his former opposition to busing, or at least soften and rationalize it? Or would he reassert his position against busing on the grounds that the policy interfered too much in the private lives of families (a position well in line with pre-Obama liberalism)?

The first choice would accept the terms of Harris’s accusation. It would also veer into leftist social engineering. The second choice would stick with the standard liberal compromise that favors equality in social affairs but holds back from intruding too far into the private sphere.

This was a key moment in the Democratic campaign. Would anyone resist the identity politics side of the party, which had claimed all the other leading candidates? Would Biden offer voters an alternative to the fixation on race and victimhood that the others were advancing on the stump?

Here is what Harris said after an opening statement about her own experience of being bused to school in Berkeley when she was a child:

But Vice President Biden, do you agree today, do you agree today that you were wrong to oppose busing in American then? Do you agree?

And here is how Biden responded:

I did not oppose busing in America. What I opposed is busing ordered by the Department of Education. That’s what I opposed.

When Harris brought up the Voting Rights Act, the Civil Rights Act, and the Equal Rights Amendment (ERA), Biden maintained his self-defense:

I have supported the ERA from the very beginning when I ran—I supported the ERA from the very beginning. I’m the guy that extended the Voting Rights Act for 25 years. We got to the place where we got 98 out of 98 votes in the United States Senate doing it. I have also argued very strongly that we, in fact, deal with the notion of denying people access to the ballot box. I agree that everybody wants the—anyway, my time is up, I’m sorry.

His response amounted to one thing: “No, no, I’m not a bad guy—I’m a good guy, really I am.” It was hard to watch. This was a time for vigor and conviction, which Harris certainly possesses, not dithering and explanation. But Biden couldn’t hold firm. He forgot a fundamental rule of debate: when someone attacks you, don’t explain yourself; you must turn the allegation back upon the accuser.

Here is what Biden might have said: “Senator Harris, while you were a child, I was supporting the very programs that gave you the opportunities that brought you to the Senate. To push for busing back then would only have increased public reaction against programs of racial justice and hurt you and your family. Busing was one of the most unpopular policies ever devised. I opposed it then, I oppose it today, and I’ll oppose it tomorrow.”

Had he done so, Biden would have jumped 10 points among Democrats. He might also have peeled off working-class white voters from President Trump who are sick and tired of being condemned as bigots. But he couldn’t do it. His forgettable reply proved that the old liberalism from which Biden took his politics is in permanent retreat.

Democrats can’t be Martin Luther King-style, content-of-character liberals anymore. They can’t hold to the liberal premise of individual rights, not when group identity has become the first determination of who and what a person is. Liberalism has succumbed to leftism. Joe Biden has gone so far as to say that males who identify as female and who commit crimes should be jailed in women’s prisons.

Biden was Clintonian liberalism’s last chance to hold off progressive zealots Bernie Sanders, Elizabeth Warren, and Alexandria Ocasio-Cortez. He catapulted to the top of the field as soon as he entered the race precisely because many Democratic voters wanted a liberal politician who hadn’t plunged so deeply into identity politics. They preferred a figure who came off as normal, an answer to erratic characters taking up airtime—Nancy Pelosi bumbling through press conferences, Senator Cory Booker (D-N.J.) as Spartacus, Rep. Rashida Tlaib (D-Mich.) shrieking about impeachment, and Beto O’Rourke on tabletops.

They could only have shaken their heads when they heard what Biden said in an interview in August: “White folks are the reason we have institutional racism. There has always been racism in America.”

This was more like Stokely Carmichael than Bill Clinton. It failed the Democrats in 1972, and it likely will fail in 2020.

Nevertheless, the outcome is clearer every day: the old fashioned liberal has no more fight in him. He is a victim of his own liberal guilt, pressed by relentless leftists to show his fealty to the cause. It is impossible to imagine any Democratic candidate having a Sister Souljah moment, named for the time when Bill Clinton rejected the militant black denunciation of white people—and found it helped him with the voters.

Michael Bloomberg, another 20th-century liberal, couldn’t do it, either. He joined the race in November, but not before apologizing for the stop-and-frisk policies he continued in New York City after succeeding Mayor Rudy Giuliani. It was not enough to say that stop-and-frisk was a misconceived program of crime-fighting. He had to show penance:

Over time, I’ve come to understand something that I long struggled to admit to myself: I got something important wrong, I got something important really wrong. Today, I want you to know that I realize back then I was wrong, and I’m sorry.

It’s the wrong calculation, a loser’s choice, but that’s not the main problem. As liberals cave to leftists, they inch American society ever further into tribalism. They are destroying what’s left of the civic realm, making everything political, everything a competition of identities. And nobody in the Democratic Party has the will or the power to stop them.