For Zohran Mamdani, Winning Is One Thing. Governing Will Be Quite Another.

Before too long, Mayor-elect Zohran Mamdani will have to manage the possible chasm between his promises and his performance, between ambitious goals and fiscal constraints.

And he will have to do so in New York City, whose 8.5 million people, $116 billion budget and 300,000-person staff would be more than enough to challenge a new mayor without the added bonus of President Trump, who has already placed a stop on billions of dollars destined for the five boroughs.

The city can be so unruly that its outgoing mayor, Eric Adams, came up with an aphorism to describe it: “Eight million people, 35 million opinions.”

Indeed, as difficult and momentous as Mr. Mamdani’s unlikely ascent from obscure state lawmaker to mayor-elect has been, he is about to confront a fundamental political reality: Winning is one thing. Governing is quite another.

“He will have a brief fleeting moment to celebrate,” said Bill Bratton, who served as police commissioner under both Rudolph W. Giuliani and Bill de Blasio. “And then it’s going to be the agony of governing New York.”

Few candidates have set hopes quite as high as Mr. Mamdani, who won the mayoralty with soaring rhetoric about expansive new government programs. His charisma and message have made him a Democratic figure of national political importance at a time of party disarray.

Mr. Mamdani’s first order of business will be to appraise the remnants of the outgoing administration and decide who to keep and who to let go from the leadership of more than 100 offices and agencies. He will have to determine how many deputy mayors he wants and then hire them. And Mr. Mamdani has indicated that he will turn to at least some seasoned technocrats to supplement his coterie, who are mostly young and have limited management experience.

Experience does seem to matter, said Meera Joshi, a former deputy mayor for operations under Mr. Adams. “I’ll speak personally,” she said. “Really hard decisions get easier to make over time. It’s sort of like training for something. You have to do it a lot until you get better at it.”

Mr. Mamdani will also have to decide whether to involve himself in the ongoing race for speaker of the New York City Council — the person who will be his governing partner — and he will have to cobble together a preliminary budget plan in January.

More broadly, he will have to figure out how to enact his agenda of universal day care, free and fast buses, and rent freezes for stabilized tenants in a state run by a governor, Kathy Hochul, who opposes the tax increases he is seeking to fund his plans and who will be running for re-election next year against a close ally of Mr. Trump.

He will also have to ensure that crime does not start trending upward, because, Mr. Bratton said, critics will be watching the crime statistics “like a hawk.” And he will have to manage a Police Department that in years past he described as “racist” and “wicked.”

All the while, he will have to deploy his formidable communication skills to moderate New Yorkers’ expectations, even if that was not his message on election night.

“When we enter City Hall in 58 days, expectations will be high,” he said in his victory speech. “We will meet them.”

Vincent Cannato, an associate professor of history at the University of Massachusetts Boston, wrote a book about New York under John Lindsay, another unusually charismatic and idealistic young mayor who reminds him of Mr. Mamdani. He called it, “The Ungovernable City,” and described the New York City of today as “limping along” and “adrift.”

He sees echoes of Mr. Lindsay’s ideological rigidity in Mr. Mamdani, which he predicted would pose problems.

“Compromise was not really Lindsay’s strong suit. He was not built that way; he was a moralistic politician,” he said. “In terms of urban politics, pragmatism is very important.”

But there are also risks to compromise, chief among them alienating one’s political base.

The mayor-elect has made well-documented overtures to the business world, telling leaders in private meetings that he would discourage the use of the phrase, “globalize the intifada,” and was open to funding his proposals by means other than tax increases. He has also offered to keep Jessica Tisch, scion of a billionaire New York family, as police commissioner.

So far, none of these moves have angered Mr. Mamdani’s base. But Gustavo Gordillo, the co-chair of the New York City Democratic Socialists of America, said there was a line that Mr. Mamdani could not cross.

“Siding with the 1 percent over his base and the rest of the city is what would really pose problems to his governing coalition,” Mr. Gordillo said.

There is a reason the mayoralty of New York City is often referred to as the second hardest job in the country, after the presidency. Aside from the basics, like teaching about 900,000 public school students and disposing of 24 million pounds of refuse a day, mayors must also confront unexpected challenges of monumental proportions.

As mayor, Michael R. Bloomberg led New York City’s recovery after Sept. 11, only to see the economy crash in 2008 and a devastating hurricane in 2012. Mr. de Blasio managed the American epicenter of the coronavirus pandemic in 2020. Mr. Adams saw the city out of Covid, only to manage an influx of migrants from the southern border.

“You’re making escape-room level decisions every day, multiple times a day,” said Ms. Joshi, the former deputy mayor who resigned from the Adams administration after the Trump Justice Department moved to dismiss corruption charges against the mayor in apparent exchange for deportation help. “By the time it gets to the mayor, they’re the hardest of the hardest problems and the stakes are high and neither way is going to be an easy path.”

There is also the omnipresent shadow of Mr. Trump, who has threatened to send troops to New York City, has promised to cut federal funding to New York once Mr. Mamdani takes office and has inaccurately called him a communist.

“If Communist Candidate Zohran Mamdani wins the Election for Mayor of New York City, it is highly unlikely that I will be contributing Federal Funds, other than the very minimum as required, to my beloved first home,” Mr. Trump said on social media on Monday.

Linda Sarsour, an old friend of Mr. Mamdani’s and a co-founder of the Muslim Democratic Club of New York, expressed hope that New Yorkers would give Mr. Mamdani time, even as she worried that his youth, religion, ethnicity and democratic socialist identity would prompt the opposite response.

“The challenge is governance, who he brings on to the team and whether or not people will give him the grace that he deserves to make City Hall aligned with his values,” she said. “And I don’t know if a candidate like Zohran is going to get the grace that he deserves.”