Joe Biden’s electoral turnaround is the swiftest and most dramatic in modern American politics. Only a day before the South Carolina primary, his candidacy was on life support. Then came Rep. Jim Clyburn’s crucial endorsement, along with his tough-love message for the candidate to stay focused. Clyburn is a formidable figure in his home state and the highest-ranking African American in the House of Representatives. His word carries weight. The weight it carried this time was Joe Biden’s quivering body, which had been left for dead. It helped him win a thumping victory in South Carolina and gave him extraordinary momentum for Super Tuesday, only three days later.

Biden’s unexpectedly strong showing has made him the party’s the presumptive nominee. His remaining opponents in the center lane, Amy Klobuchar, Mike Bloomberg, and Pete Buttigieg, not only dropped out, they endorsed the former vice president, as did Beto O’Rourke. Expect more high-fives to follow as the bigwigs and donors fall in line. As the old Chicago machine pols used to say, “Don’t make no waves. Don’t back no losers.” They saw Bernie Sanders as a loser, and a dangerous one at that.

The betting markets endorse Joe, too. His odds of winning the nomination are now over 85%. Bernie’s are under 10%. Only recently, before South Carolina, Sanders had been the clear favorite. No more. If he loses Tuesday’s primary in Michigan, his position will be dire. No turnaround has been more dramatic—or more helpful for party insiders—than Biden’s.

The prospect of Bernie Sanders at the top of the ticket filled those insiders with dread. How could any Democratic candidate for a purple House district in Pennsylvania, Ohio, or Wisconsin win without renouncing the party’s nominee for president? How could Democrats win the suburban vote by asking families to give up their health insurance and pay most of their income in taxes? They couldn’t. That’s why incumbents and party professionals are delighted to see Bernie heading for the ash heap of history, free to spend his time reading “Das Kapital.”

Mainstream Democrats won’t have long to relish that victory, or Elizabeth Warren’s welcome exit from the race. They will glance around furtively and notice two things above all. First, the candidate left standing is a deeply flawed one, well past his “sell by” date. Second, their party has moved so far left that an outright socialist almost won the nomination, twice actually, and the left’s strong position in the primaries forced centrist candidates to take extreme stances that will hurt them in November.

Donald Trump will aggressively exploit those unpopular positions on fracking, gun control, third-term abortions, eliminating school choice, decriminalizing illegal immigration, and supporting sanctuary cities. He’ll have the advantage of Joe Biden on tape, trapped by his own words, explaining why he backs those policies. And he can expect Joe to make plenty of miscues as he does so.

The early campaigning showed that about 35%-40% of Democratic primary voters preferred a hard-line socialist, someone whose ideology (and anger) has been frozen in amber since the 1968 riots. Since then, Sanders’ only ideological shift has been to pander about open immigration, which appeals to modern Democrats but contradicts his otherwise-strict socialist stance. Yet it was Sanders, not Biden or the other center-left candidates, who created real enthusiasm on the campaign trail, who filled the rallies, who galvanized the passionate youth. If he loses to Biden, as expected, the obvious question is whether his supporters will show up and vote for the nominee, who doesn’t light their fires or champion their policies. They could ask themselves, “What difference does it make?” and stay home.

It’s unclear whether those who cheered for Bernie really supported his agenda or simply believed he was authentic and determined to push that agenda, whatever the costs. That’s why Alexandria Ocasio-Cortez and other members of “the squad” were such a perfect fit for him. They are all self-righteous zealots who couldn’t organize a two-car funeral, hell-bent on smashing the most successful economy in world history and running the largest organization ever assembled, the U.S. government. What could possibly go wrong?

Although Democratic leaders escaped that catastrophe, they must be concerned that the party’s most active constituency has not flinched from calling itself “socialist.” No one would use the term “enthusiastic” to describe support for any other Democratic candidate, not now and not in 2016. Biden, like Hillary Clinton, is a "let's settle for this" choice. No new ideas. No real enthusiasm. No strong agenda, other than the traditional party platform, plus Obamacare.

This lack of enthusiasm is apparent in the primary vote totals, where turnout was mediocre. In some primaries, such as Texas, the Democrats combined received fewer votes than Trump did in an uncontested primary with no statewide contest to motivate Republicans. That pattern is not unique to Texas, and it’s bound to worry Democratic Party professionals.

The party will also have to confront its legacy of “identity politics.” That’s not just because the final multi-candidate debates were all white and the two remaining candidates are elderly men. It’s because the party has painted itself into an awkward corner. When the last two female contenders, Warren and Klobuchar, dropped out, House Speaker Nancy Pelosi voiced the standard rhetoric, citing an “element of misogyny” for sinking the women. That’s perfectly in tune with the party’s identity politics, but it’s hardly helpful to Biden as the presumptive nominee. It’s never wise to condemn your own voters. They are the ones, after all, who picked Biden instead of Klobuchar, Warren, Kamala Harris, Kirsten Gillibrand or Tulsi Gabbard. It wasn’t misogyny that forced Klobuchar to endorse Biden, and it won’t be misogyny when Pelosi endorses him soon, either.

In one sense, identity politics isn’t new. The old city machines were built on differential appeals to voters in Irish, Italian, black, and Jewish neighborhoods, handing out city jobs to the ethnic leaders who rounded up the votes. All politicians seek support from ethnic, racial, and religious groups and tailor their appeals to them. Bob Dylan captured those appeals when he wrote (in 1963) that “the man on the stand he wants my vote”

He's out there preachin' in front of the steeple

Tellin' me he loves all kinds-a people

He's eatin' bagels

He's eatin' pizza

He's eatin' chitlins

But today’s Democratic Party is doing more than eating collards or Impossible Burgers. It has ramped up its support for each group’s most strident complaints about the others, especially men and “white privilege.” The common theme is America’s indelible “structural” defects—its racism, xenophobia, sexism, Islamophobia, and more. It’s mourning in America.

This dark vision, which unifies the party’s left wing, depicts our history as one of shame, degradation, and exploitation. We are wealthy only because we made others poor. We are free only because we enslaved others. We are hypocritical when we think of America as “a shining city on a hill,” an example for others.

Although that vision incorporates some hard, undeniable truths, it distorts American history. It ignores the triumphs, the voters’ desire for uplift, and the widely shared goal of social integration, beyond race, creed, religion, national origin, gender, and sexual orientation. It abandons our national motto of “E Pluribus Unum” and the unifying message it represents.

Fortunately, Joe Biden is not burdened with those excesses or the party’s divisive identity politics. Unfortunately, he is burdened with plenty of other problems. His supporters will agonize every time he makes a gaffe, not only because each misstatement is embarrassing but because voters wonder if he’s a brick or two short of a full load. Many fear he is suffering cognitive decline and that it will become an issue in the campaign (or in office). He is certain to be tagged with his legacy of ill-chosen votes and speeches.

Biden’s main asset is not his intelligence, wisdom, policy savvy, good judgment, positive agenda, or voter enthusiasm. For now, it is simply that he is not Trump and not Bernie. That's not a strong platform. The question is whether he can buttress it, build a coherent, positive message, and bring voters to his side. The election hinges on it.