Moderate Democrats, business leaders, and Republicans — concerned about the prospect of a Mayor Zohran Mamdani — are plotting ways to keep the Democratic Socialist out of Gracie Mansion.

Shocked by the 33-year-old state assemblyman’s upset win in the Democratic mayoral primary last night against a former New York governor, Andrew Cuomo, these Cuomo backers, reluctant Cuomo backers, independents, and Republicans say the only way to beat Mr. Mamdani is to all back one candidate.

“The horse they’re going to back is Eric Adams,” a grocery store magnate and former Republican candidate for New York City mayor, Jon Catsimatidis, tells The New York Sun. “He is backed by the White House, by Washington, and he’ll make sure crime is cleaned up.”

When asked what that means for the Republican nominee for mayor, Curtis Sliwa, whom Mr. Catsimatidis employed at his radio station, the billionaire replied, “He’ll clean up the crime.”

Mr. Catsimatidis ended the call. He didn’t respond to a text asking if he is personally planning to back Mr. Adams. He said to tune into his radio show this evening.

Mr. Catsimatidis told the press earlier this month that he may sell his grocery store empire or move his business out of the city if Mr. Mamdani becomes mayor. Mr. Mamdani is promising to make buses and childcare free of charge, freeze rents on subsidized apartments, and open a network of city-owned grocery stores.

There are at least four candidates running for mayor in the general election. Mr. Mamdani will be running in November on the Democratic and Working Families Party lines. Mayor Adams, a Democrat, declined to run in the primary and is running for re-election on two independent lines he created. The Guardian Angels founder, Mr. Sliwa, is running as a Republican. A former United States attorney, Jim Walden, is running as an independent.

Mr. Cuomo may also run on an independent line he created, “Fight and Deliver,” though he said in a statement that he wants to “look at all the numbers as they come in and analyze the rank choice voting” before making a decision.

Mr. Mamdani got more than 432,305 first-round votes in the Democratic primary last night. Turnout in the 2021 mayoral general election was 1.1 million. That means that, if turnout is similar to the last mayoral election, Mr. Mamdani walks in with one-third of the vote already locked in — not including the second-choice votes he likely got or the votes he will earn from those who faithfully vote party line.

“Everybody right now is in panic mode,” the president of Empire State Properties, Suzanne Miller, tells the Sun. “I think that all the money is going to start pouring in for Eric Adams.”

When asked whether she thinks the Republican Party will force Mr. Sliwa to step out of the race — or at least try — by offering him a another position, Ms. Miller replied, “Yeah, I do.”

When the Sun contacted Mr. Sliwa about a potential deal with Mr. Adams, Mr. Sliwa responded by text, saying, “No one has reached out to me.”

The chairman of the Queens County Republican Party, Anthony Nunziato, tells the Sun he hasn’t heard of any plan for his party to drop Mr. Sliwa and back Mr. Adams. “Right now we’re pushing totally for Sliwa,” he said.

A Manhattan Institute poll released last week, which like all primary polls was off, envisioned a four-person general election race were Mr. Mamdani to win the primary. In that scenario, Mr. Mamdani wins with 33 percent of the vote, to Mr. Adams’s 19 percent, Mr. Sliwa’s 16 percent, and Mr. Walden’s 5 percent. Nearly 30 percent of voters were undecided. if Messrs. Adams and Sliwa were to join forces, they could beat Mr. Mamdani.

“The smart guys have to get together and pick ONE candidate to back in the general,” a right-wing author and firebrand, Ann Coulter, posted to X. “Cuomo’s dead and Sliwa’s ridiculous. Move on. I say Eric Adams.”

Mr. Adams went on “Fox & Friends” this morning to pitch himself as the commonsense, crime-fighting moderate. “He’s a snake oil salesman. He will say and do anything to get elected,” he said of Mr. Mamdani. 

Backing Mr. Adams, though, may be a bridge too far for some Democrats, who worry that he made a quid pro quo arrangement with President Trump to get the federal charges against him dropped. Yet a Democratic Socialist mayor who refuses to condemn the phrase “globalize the intifada” is also unpalatable to moderates.

“I had serious concerns about Assemblyman Mamdani before yesterday, and that is one of the reasons I endorsed his opponent. Those concerns remain,” a Democratic congressman of Long Island, Tom Suozzi, posted to X.  

The Senate minority leader, Chuck Schumer, posted to X that Mr. Mamdani ran “an impressive campaign,” but he didn’t endorse the new Democratic nominee. Another New York Democrat in Congress, Laura Gillen, also expressed concerns about Mr. Mamdani in a statement on X.

“Socialist Zohran Mamdani is too extreme to lead New York City,” she posted. “Mr. Mamdani has called to defund the police and has demonstrated a deeply disturbing pattern of unacceptable antisemitic comments which stoke hate at a time when antisemitism is skyrocketing.”

It’s unclear who these Democrats will back in the race, if anyone. A hedge fund billionaire, Bill Ackman, who donated half a million dollars to Mr. Cuomo’s super PAC, posted to X Wednesday that he “was a bit depressed when I woke up” but has “a great idea on NYC.” He later posted that it was about “legal issues concerning the potential for another candidate to run now.”