The 33-year-old Mamdani was, until recently, a little-known state assembly member and came into the Democratic primary as an underdog, unlikely to surmount former Gov. Cuomo’s brand recognition and billionaire backers. But his proposals—which included rent freezes, free bus fare, and city-owned grocery stores—ultimately resonated with New Yorkers who have faced rising rents and heaps of economic pain in one of the most expensive cities in the world.

Mamdani has all but clinched the nomination after Cuomo conceded the race this week, and because of his democratic socialist label and controversial proposals, billionaires have rushed to paint the young politician as a threat to business, democracy, and the Democratic Party. Many of the billionaires protesting also lost financially, donating to Fix the City, a nonprofit group that received about $25 million in donations and spent loads on pro-Cuomo ads and anti-Mamdani ads, per Business Insider.

Here are some of the loudest (and richest) voices attacking Mamdani after his landmark win. 

Bill Ackman (Net worth $8.09 billion)

One of the loudest voices condemning Mamdani is activist investor and hedge fund manager Bill Ackman. Ackman, who founded Pershing Square Capital Management, let loose on Mamdani in one of his characteristic posts on X. 

In response to Mamdani’s win, the hedge funder said he and his allies would saturate New York City’s election with donations to try to defeat him. 

After calling Mamdani “young and charming,” Ackman criticized him for his comments about the New York Police Department, and his proposals for rent freezes and city-owned grocery stores. He also claimed a Mamdani mayoral victory would push Big Business to exit New York. 

“Socialism has no place in the economic capital of our country,” wrote Ackman on X. “The ability for NYC to offer services for the poor and needy, let alone the average New Yorker, is entirely dependent on NYC being a business-friendly environment and a place where wealthy residents are willing to spend 183 days and assume the associated tax burden.”

Ackman also promised hundreds of millions of dollars in funds “will pour in” if the right candidate to oppose Mamdani appears.

Elon Musk (Net worth $368 billion)

Now essentially on the sidelines of government after running President Trump’s Department of Government Efficiency, Tesla CEO Elon Musk still found time to chime in on Mamdani’s win, even if he held back major criticism. 

In several comments reacting to other users’ tweets on X, Musk made his skepticism about Mamdani known. Musk delivered a laughing emoji in reaction to another user’s post criticizing Mamdani and saying, “Queer liberation means defund the police.” 

John Catsimatidis (Net worth $4.5 billion) 

The billionaire founder of the Gristedes grocery chain threatened to move the company out of New York should Mamdani win the NYC mayoral election, relocating the company’s corporate offices to New Jersey.

“If the City of New York is going socialist, I will definitely close or sell or move or franchise the Gristedes locations,” Catsimatidis told Fox Business.

Catsimatidis also took issue with Cuomo and the way he ran his campaign. 

“It’s not a done deal, but Cuomo screwed up real big because he tried to do what President Biden did and hide in the basement for two months,” Catsimatidis told Forbes.

However, the grocery chain magnate said Trump may be able to help current New York City Mayor Eric Adams beat out Mamdani in the general election in November. Adams has vowed to run as an independent.

Dan Loeb (Net worth $3.2 billion) 

Dan Loeb, the billionaire founder of hedge fund Third Point, donated $250,000 to support Fix the City, which backed Cuomo. 

After Mamdani’s presumptive win, Loeb criticized New York Gov. Kathy Hochul’s comment calling Mamdani’s campaign a “formidable grassroots coalition.”

“For anyone who had a doubt that our Governor is a clueless, unqualified buffoon,” Loeb said in a post on X.

Loeb also cheekily declared: “It’s officially hot commie summer.”