He’s in no Mam’s land.

Longtime state Democratic Party leader Jay Jacobs refused to back Zohran Mamdani for New York City mayor Thursday — and could step down over Gov. Kathy Hochul’s stab-in-the-back endorsement of the far-left pol, sources said.

Jacobs bucked Hochul in a pointed statement, saying he had unbridgeable differences with the Democratic nominee, while acknowledging that fear-mongering over the socialist’s ascendance was “wrong and a gross over-reaction.”

“Mr. Mamdani and I are in agreement that America’s greatest problem is the continued growth in income disparity in our nation. On how to address it – we fundamentally disagree,” his statement began.

“Furthermore, as I expressed to him directly, I strongly disagree with his views on the State of Israel, along with certain key policy positions,” Jacobs said.

“I reject the platform of the so-called ‘Democratic Socialists of America’ and do not believe that it represents the principles, values or policies of the Democratic Party. For those reasons I will not be endorsing Mr. Mamdani for Mayor of the City of New York.”

The searing anti-endorsement came amid swirling rumors that Jacobs would resign after Hochul jumped on the Mamdani bandwagon Sunday evening — furthering the highly unusual divide between a sitting governor and their party’s chair over who should be the city’s next mayor.

Sources said Jacobs — who also serves as the Dems’ chair in Nassau County, where the party has been hemorrhaging support and Mamdani is unpopular — was furious over Hochul’s endorsement and likely would head for the exit.

“She’s putting him in a bad situation,” said a party official, who asked not to be named. “The governor is trying to get him to stay on, but he’s saying he’s not going step back and be for this guy who is against Jews.

“How does Jay Jacobs win in Nassau County? You’re almost going to force him to resign,” the source fumed. “Do you stay a state chairman or lose your local party? And how does the state chairman not endorse the largest city’s Democratic pick?”

One source close to the situation said Hochul was trying to talk Jacobs off the ledge, but the damage was done.

Another source close to the state’s Democratic Party said those rumors appeared greatly exaggerated and that they expected Jacobs to stay put.

In a statement, a Hochul campaign spokesperson said: “The governor and party chair have not discussed his tenure since his statement today. As the leader of the party, the governor is holding ongoing discussions about who the best person is to serve as chair moving forward.”

The split between Hochul and Jacobs signifies a growing rift between moderate and left-wing Empire State Democrats. 

State Sen. Mike Gianaris, the No. 2 Democrat in the upper chamber of the Legislature, called Jacobs’ “disgraceful.”

“The Chair of the Democratic Party refusing to support the candidate clearly selected by the voters of the Democratic Party,” Gianaris posted on X. “If he won’t perform that most basic responsibility of a party leader, what exactly is he doing over there?”

A Dem party official seethed: “Jay publicly hates democratic socialists and it seems wildly out of touch to even consider staying on as chair given the circumstances.”

Jacobs was elected Democratic Party chair in 2019, under then-Gov. Andrew Cuomo, after serving in the position roughly a decade earlier.

After Cuomo resigned in 2021, his successor Hochul stuck by Jacobs, who’s widely seen as the voice of moderate suburban Democrats.

But progressive and Democratic Socialists of America-aligned pols have been unhappy with the moderate Jacobs, blaming him for Dems’ poor 2022 midterm elections showing and calling for Hochul to oust him.

Hochul, who is close to Jacobs, kept him on – but their split over Mamdani could present problems for Democrats, especially on Long Island, where Reps. Tom Suozzi and Laura Gillen face strong challenges to their swing seats. Both have been vocally opposed to Mamdani.

Former Gov. David Paterson, who served as the Dems’ chair under part of Cuomo’s tenure, said Jacobs’ statement looked like a “rebuke” of Hochul, at least on the surface.

“Jacobs’ statement reads like ‘I agree with Mamdani that it’s sunny and it’s a sunny summer day,’ and agree on nothing else,” he quipped.

Paterson said the statement indicates a left-moderate schism in the party that must be dealt with after November’s election.

He joked that then-Gov. Cuomo would have not tolerated such dissent from his party chairman over a major endorsement.

“Gov. Cuomo would have my head,” he said.

Sources complained that Jacobs also made the extremely brazen move of allowing Cuomo access to the party’s voter database, known as NGPVAN, after the ex-gov lost the Democratic primary to Mamdani and declared his independent run for mayor.

Mayor Eric Adams also has access even after he abandoned the Democratic primary to run as an independent.

A source familiar with the situation said Cuomo and Adams purchased the access to NGPVAN and that contracts for the service typically run through the general election.

Still, sources fumed that Jacobs was undercutting his own party’s nominee.

“It’s despicable and he shouldn’t be allowed to step down,” one longtime party official said. “He should be run out of town on a rail.”