Billionaire Bill Ackman announced he is backing Andrew Cuomo in New York City’s mayoral race — in a dramatic about-face after he previously endorsed Mayor Eric Adams, claiming the former New York governor did not have the energy to defeat surging socialist Zohran Mamdani.

“Eric has been a charismatic and high-energy leader who has shown real empathy and provided critical moral and other support to NY communities in their time of need,” the hedge fund titan wrote in a late-night X post Thursday.

“All of that said, Eric should step aside and not run for reelection. Eric’s polls have deteriorated substantially since the primary, and it has become increasingly clear that he does not have a chance to beat @ZohranKMamdani.”

Just two months ago, Ackman had endorsed Adams and called on Cuomo to drop out of the race, claiming his “subdued energy” made it “abundantly clear” that the ex-governor “is not up for the fight” to take down Mamdani.

But Ackman — who donated $500,000 to Cuomo’s failed Democratic primary campaign — has perhaps sensed a change in the wind just 60 days before Election Day.

The latest polls have Adams lagging in the single digits — down from the mid-teens around the time of the primary, in which he failed to muster any meaningful support as his corruption scandals still loomed large.

Cuomo, meanwhile, is polling in the mid- to high 20s while front-runner Mamdani’s support has stalled in the high 30s to low 40s.

“There is a lot that needs to be improved in New York City. @andrewcuomo is an experienced leader that cares deeply about our city who has the relevant experience and skills necessary to lead and greatly improve NYC,” Ackman said.

“Andrew had major accomplishments as our governor. He also made some mistakes. I am a huge believer in backing leaders who have learned from their mistakes and have something to prove,” he said in apparent reference to Cuomo’s sexual harassment allegations that forced him out of the governor’s office in 2021.

Cuomo has denied the allegations.

Ackman acknowledged that Adams has done a “good job” leading the Big Apple, noting the city’s strong economy, declining crime and his handling of the migrant crisis — but he believes Cuomo is best suited to “win in a two-horse race with Adams’ help” from the sidelines.

“Mayor Adams, it is time for you to play a critical role in NYC’s future by gracefully stepping aside to enable Andrew to win,” Ackman said.

“We will all be eternally grateful.”

White House officials have been discussing potentially giving Adams a plush gig in the Trump administration, including a possible ambassadorship, to get him out of the mayoral race as his polling numbers plummeted, The Post learned this week.

A source in the mayor’s orbit confirmed his team has pushed him to take the position — but Adams does not seem ready to throw in the towel yet.

“I have a job. I’m running for re-election, I’m still doing that and I’m looking forward to getting re-elected,” Adams said at an unrelated press conference Wednesday when asked about the rumors.

Trump officials have also been urging GOP mayoral nominee Curtis Sliwa to drop out — and even offered him a position in the administration — but he has refused as donors fill his campaign coffers.