Love him or hate him, it’s undeniable that New York City Mayor Zohran Mamdani is about as likeable and charismatic as it gets. With that behind him, he took the city by storm with his childlike fantasy of free stuff and smiles. After all, who doesn’t want free stuff from a happy guy, right?

But if he gets his way, his endorsed candidates for Congress, comrades Claire Valdez and Darializa Chevalier, Democratic-Socialists both, will fracture the Democrats into the ineffectual party that gave rise to the MAGA delusions. And Mamdani is good with that.

The mayor’s support goes further than mere endorsements. With his popularity never higher, Mr. Mamdani has personally involved himself in everything from candidate recruitment and fund-raising to ad shoots and private strategy sessions. A pair of his top political aides are helping run two of the campaigns. And the mayor attempted to push labor unions into backing at least one of his candidates.

These primary candidates not only share Mamdani’s hatred of Israel, but his fantasy that the rich, the corporations, the landlords, can be taxed into oblivion and the monies raised will provide a laundry list of free benefits for the poor and working class. You know, everything that gave rise to the election of the polar opposite in Trump, who played off the claim that the Dems were all radical commie leftists who wanted to destroy America. Mamdani wants to prove Trump right.

There is no real recent precedent for such an aggressive mayoral posture in off-year elections in New York City. Michael R. Bloomberg and Bill de Blasio got involved in State Senate contests when each was mayor. But modern mayors have tended to want to broaden their political coalitions while governing, not risk shrinking them.

Mr. Mamdani and his allies argue that no one should be surprised that a mayor who stormed into office by ignoring old political conventions and challenging more seasoned candidates would take on more risk now.

Mamdani has a point; he never claimed any pretense to moderation or getting along with anyone else in the Democratic Party. It should come as no surprise that liberals are just as much, if not more, the enemy as MAGA. But even the progressive wing is far too moderate for Mamdani and his chosen candidates.

Suddenly, the progressive Democrats are realizing the danger presented by the possibility of representatives far more radical than they are.

Tensions really began to rise, though, when [Congresswoman Nydia] Velázquez, an early Mamdani supporter, announced her retirement after three decades in the district Mr. Mamdani won overwhelmingly.

Ms. Velázquez hoped that one of her protégés (including some who are members of D.S.A.) might succeed her, but Mr. Mamdani batted those possibilities away in favor of Ms. Valdez. She was only in her first term as a state assemblywoman, and Ms. Velázquez barely knew her. But she was an early supporter of his mayoral ambitions and another critic of Israel.

The congresswoman was furious. “I’ve never heard her use more four-letter words,” Letitia James, the state’s attorney general, said.

Most moderates would find Velázquez a bit too left for their taste, and yet here she is, stuck in the middle with you.

The resulting race has driven a wedge between socialists and progressives and exposed painful questions tied to the area’s rapid gentrification. Ms. Velázquez and the Working Families Party have accused the D.S.A. of trying to push them aside while capitalizing on their long-term organizing. The socialists say the progressives are not meeting the moment.

While it might seem counterintuitive, nothing has helped the DSA more than the election of Trump as president. His corruption and incompetency provides the template for the election of “anyone but Trump,” which is the only way hard left socialists could get elected to office. Of course, the progressives did the same for Trump, enabling him to run against woke despite the experience of corruption and incompetence in his first term. This is the pendulum of bad choices, except it’s now swinging even harder left and right than ever before.

As some might realize, I’m not a big fan of Trump, and would very much like to see a Democratic-majority Congress to try to prevent his worst and most dangerous impulses, nominees and unlawful actions. But what will happen should the Democrats elect a cadre of socialists is that they will be held captive to the extremes of their own party in order to muster a majority to prevent Trump from indulging his dotage whims.

If the Democrats can’t put together a majority without throwing bones to its left-most fringe, the handful of radicals as endorsed by Mamdani will be in a position to exert inordinate influence that will alienate liberals and moderates, as well as the MAGA types who hate the Dems regardless. Can the Democrats prevail in the midterms? Yes they can. They can also grasp defeat from the jaws of victory if they refuse to reject the radical fringe that is using Trump, and them, to gain the power they could never gain on their own. Don’t let it happen.