Reihan Salam has a lot in common with the man he is trying to stop.

They went to rival New York City public high schools. Both are South Asian Muslim men with a talent for remembering faces and names. Mr. Salam, the head of the conservative Manhattan Institute, and his democratic socialist foil, Mayor Zohran Mamdani, both favor merch embroidered with the same 1970s cursive City of New York insignia.

They share something else. They are convinced that their beloved city is in crisis. For the mayor, the crisis is affordability. For Mr. Salam, the crisis is Mr. Mamdani.

“You have a couple of decades of prosperity that are slipping away,” said Mr. Salam, 46, who lives with his family in a Brooklyn neighborhood that voted overwhelmingly for Mr. Mamdani. “We are squandering this incredible opportunity to show that urban life can work.”

He fears that many of his fellow New Yorkers have been seduced by what he sees as the mayor’s vilification of the city’s wealthiest residents and misled by Mr. Mamdani’s vision of free buses, free child care and frozen rent. He believes the mayor’s big plans to subsidize the costs of city life for even well-off New Yorkers (“unlimited welfarism for the near-rich,” Mr. Salam calls it) could steer New York City into a financial tailspin reminiscent of the dark days of the 1970s.

To counter all that, Mr. Salam is trying to make the Manhattan Institute, a think tank with a roster of New York City obsessives, the intellectual engine of the resistance.

Slowing down the mayor and his popular movement will be no easy task, as others have discovered. The city’s vaunted business elite spent tens of millions of dollars trying to persuade voters that Mr. Mamdani’s ideas about capitalism and Israel were too radical for New York, without success. The Democratic establishment has largely been cowed by the mayor’s political strength. Elected Republicans are so outnumbered in New York that they have no real power to stop him.

Neither does the Manhattan Institute. Over a half-century, the organization has lobbied constantly for shrinking the city’s sprawling bureaucracy and letting private industry work its magic. The election of a democratic socialist marks a low point for the institute in New York, where its project has never been further from the halls of power.

But Mr. Salam, its president since 2019, sees an opportunity. Mr. Mamdani’s electric campaign has created unusual interest in big ideas about what works, and what doesn’t, when it comes to administering government in the city.

Where some right-wing critics have caricatured the mayor as a communist, a jihadist and a candidate for deportation, Mr. Salam and his fellow conservative urbanists are testing a less hyperbolic approach. They have taken direct aim at Mr. Mamdani’s policy agenda, deploying deep knowledge of city history and policy expertise to try to serve as a voice of skepticism whispering in the city’s collective ear.

Do people making hundreds of thousands of dollars a year really need free child care?

Might a rent freeze cause even fewer people to leave their apartments, driving the vacancy rate so low it could destabilize the housing market?

Could free buses turn the M4 into a daytime shelter for homeless people?

The mayor’s office declined to comment on the Manhattan Institute. Mr. Mamdani has said he believes it is government’s job to deliver excellent services rather than choose who receives those services, especially in the face of the city’s affordability crisis. In his inaugural address, the mayor took on critics of “big government,” saying, “No longer will City Hall hesitate to use its power to improve New Yorkers’ lives.”

Changing the mayor’s worldview may be out of the question. But if Mr. Salam and his group of warrior-wonks can influence other pillars of the New York cognoscenti — activists, nonprofit leaders, city commissioners, journalists — they hope it might be just enough to slow down the big-government bandwagon.

“I vehemently believe that we are defenders of the beautiful mosaic,” said Mr. Salam, using a twist on a phrase coined by David N. Dinkins, a former Democratic mayor, to describe New York in all its glorious complexity.

“But it means that you need to not be an idiot.”

‘I try to be constructive’

A half-century ago, the mosaic was seriously blighted.

Decades of poor fiscal management had left the city teetering on the edge of total financial collapse, and signs of New York’s imminent demise were everywhere. The subways were covered in graffiti, muggings were common, trash piled up on the sidewalks and streets, some landlords set their buildings on fire for the insurance money and a 25-hour blackout led to widespread looting.

These days, the city is not in pristine financial health. Fiscal experts estimate that New York will face significant budget deficits within the next few years. But the city and state set up guardrails decades ago to avoid a repeat of the irresponsible accounting and financial chaos of the 1970s.

The Manhattan Institute is not expecting another financial emergency to set in tomorrow. Still, to Mr. Salam and his colleagues, the ’70s fiscal crisis is not so much a historical event as a scriptural one — a Great Flood whose legacy should serve as a permanent warning to the city’s leaders that things can go terribly wrong when government spends more money on social services than it can actually afford.

A few weeks after Mr. Mamdani was elected last year, a crowd assembled at the institute’s headquarters around the corner from Grand Central Terminal for a panel titled “The Fiscal Crisis at 50: Lessons for a New Era of City Government.” The room was so packed that even Dean Fuleihan, a longtime Democratic Mr. Fix-It who had just been named Mr. Mamdani’s most senior aide, had to hunt for a seat.

In an impromptu exchange with the panelists, Mr. Fuleihan said the reforms that had been put in place to prevent future fiscal calamities were “making my life easier.”

“It is the responsibility of government to listen to the opinions of the people they serve, even when it leads to spirited discussions about the 1975 fiscal crisis,” Mr. Fuleihan told The New York Times in a statement.

Getting a consigliere of the mayor to show up at its office for any reason was a good sign for the Manhattan Institute and its efforts to start a conversation that city leaders might actually engage in.

The think tank, created in 1978, has always had a broader focus than New York. Many of the organization’s 85 scholars comment on national issues, and some have taken up arms in the conservative culture wars over public safety and transgender rights. But a subset of New York-focused wonks are now working overtime to try to come up with more Manhattan Institute-y solutions to some of the problems the mayor wants to solve.

“I try to be constructive,” said Eric Kober, the institute’s local housing expert.

“It’s not enough to simply criticize him,” he added, “it’s also necessary to offer something that he could do.”

Mr. Kober, who spent 35 years working under mayors of all stripes at the city’s planning department before joining the think tank, has tried to come up with tweaks of Mr. Mamdani’s policy proposals that could save money and lean more on private business.

The mayor could, for example, roll back regulations that require local government to decide how many parking spots should be required for commercial businesses, and leave it to developers, which might encourage investment in the city. Or, instead of spending $30 million on a new municipal grocery store in East Harlem, with prices subsidized by taxpayers, Mr. Kober wrote recently, the mayor could take that money and upgrade existing small supermarkets or try to bring in more discount stores like Aldi and Lidl.

Stephen Eide, a fellow focused on social services, is hoping that he can appeal to Mr. Mamdani’s interest in “sewer socialism,” the idea that progressive government should be laser focused on improving city services. He argues that decreasing spending can actually help orient local government to the city’s most urgent problems.

“Keeping government small to us is not an end to itself,” Mr. Eide said. “It’s a larger goal of making sure that government can focus on the stuff that only government can do,” like providing better treatment for mentally ill people on the subway or responding more quickly to 911 calls.

Nicole Gelinas is a transit expert whom even some critics of the Manhattan Institute take seriously. (Brad Lander, an ally of the mayor, said he had “learned a lot” from her even if they often disagree.) She has spent the last few months honing her central thesis of the Mamdani era: The mayor has promised a vision he can’t actually deliver on. She considers it her responsibility to help reset expectations.

She has noted that Mr. Mamdani showed some fiscal restraint by backtracking on two promises he made as a candidate; he has pushed state lawmakers to delay an expensive cap on public-school class sizes and scaled back a proposed expansion of a multi-billion-dollar housing voucher program.

But finding the money for free buses and more free child care, she contends, could force the mayor to make more difficult decisions about what gets funded and what doesn’t.

“The idea that you are going to have some magic bag of tricks and the city will become affordable,” Ms. Gelinas said, “it’s just not going to happen.”

Patrick Gaspard, a top adviser to Mr. Mamdani who led the Democratic National Committee, said he had found the Manhattan Institute’s work to be rigorous and thoughtful. Its scholars, he said, are engaging in “the kind of conversation reasonable people can have about the appropriate role of government, the relationship to the private sector, what it means to general growth.”

But Mr. Gaspard took a dim view of the institute’s relevance these days.

“They have neither the political heft or the cultural currency to be consequential,” he said. “They just don’t.”

‘Someone is going to have to pick up the pieces’

It wasn’t always like that. In the 1990s, the Manhattan Institute had so much political heft that Rudolph W. Giuliani, the city’s Republican mayor, later joked about having basically plagiarized its ideas.

In those days, the group identified crime, poor city services and struggling public schools as New York’s biggest problems and helped steer city government toward solutions.

Many believe the city became safer and more functional as a result.

But the broken windows theory of policing evangelized by the Manhattan Institute, which held that the police should focus more on small crimes to prevent larger ones, exacerbated racial tensions in the city when police officers targeted Black and Latino New Yorkers at higher rates than other groups.

And the rightward pivot of the late 1990s arguably marked the beginning of the moment when New York became so desirable, and so expensive, that the city began to slip out of reach for its working-class and middle-class residents — and then for its reasonably-well off ones.

Today, Mr. Salam’s warnings about the mayor and his agenda still have an audience with the New York’s moneyed elite.

Hundreds filed into an majestic old bank building in Midtown in May for the institute’s annual black-tie fund-raising gala. Outside, protesters greeted attendees with chants of “tax the rich,” a slogan of the city’s recent political revolution. Inside the room, Mr. Salam told the assembled donors — who were paying as much as $250,000 for a table — that the protesters represented a certain view: that “prosperity is something to be handed out by the state, and that the only thing standing in between them and the lives they want is someone else’s wealth.”

The Manhattan Institute, he told them, “exists to confront this seductive lie and to stand for something better.”

Recruiting allies in other precincts of Mr. Mamdani’s New York, though, could be harder.

They are trying. Some of the Manhattan Institute’s local fellows turn out a weekly newsletter on Substack about city government, the Bigger Apple. City Journal, the Manhattan Institute’s in-house magazine, recently delivered a scoop on how one of Mr. Mamdani’s commissioners had scheduled a meeting with an Iranian diplomat without the mayor’s knowledge.

One of the institute’s fellows, Daniel Golliher, teaches his own course about New York civics, and requires his students to attend community board meetings and memorize sections of city law. The goal is to create more educated voters — and perhaps eventually city employees and politicians.

The Manhattan Institute’s credibility with fellow New Yorkers may depend on the ability of its content creators to signal that their bias is, above all, pro-New York. Mr. Salam calls himself “an aggro partisan of urban life,” and draws a line between the institute and those on the right who see the city as inherently doomed.

“We are trying to make an argument for a multiethnic, metropolitan future for the country,” said Mr. Salam, whose parents immigrated here from Bangladesh before he was born. “That is a place where others on the right see as hopeless or deserving of their misery, we affirmatively reject that.” He says New York is the only place he’s ever wanted to live, the only place he could ever live, especially because he never got his driver’s license.

Despite its New York City roots, the Manhattan Institute is unquestionably part of the national conservative landscape, in ways that may alienate some New Yorkers.

Although the institute it is not central to the MAGA movement, its work is funded by some of the same conservative megadonors who support President Trump. It produces proposals that Republicans marshal in polarizing national political fights, like recent draft legislation that would reclassify disruptive acts of protest like blocking roads as “civil terrorism” felonies. Christopher Rufo, a conservative activist and writer on the payroll, has led the movement against diversity, equity and inclusion initiatives.

Even some of its New York-focused scholars have dinged the mayor in ways that can come across as less than collaborative. Ms. Gelinas wrote a New York Post column headlined: “Mamdani acts like a petulant teen in front of the king and queen.” Another Manhattan Institute fellow wrote an article accusing Mr. Mamdani of being a “show-off,” more interested in photo opportunities “than the dirty work of governing.” And after Mr. Mamdani asked New Yorkers to keep their air-conditioners at 78 degrees during a heat wave, following the same advice as mayors before him, a Manhattan Institute fellow posted a video in which he turned his air-conditioning down to 67 degrees, while blasting the song “God Bless the U.S.A.”

Liz Krueger, an influential state senator from Manhattan, said she had stopped reading most of the think tank’s output years ago because she felt it was biased. “Too many of the far-right messengers in today’s era are nut jobs,” said Ms. Krueger, a Democrat. “I don’t know whether that includes the Manhattan Institute because that would require I actually read it.”

Mr. Salam said he does not need New Yorkers to like everything he and his colleagues say.

He imitated a serious-sounding scold who might say: “These guys are terrible, noxious, a dangerous force, but by the way, I agree with them on some things.”

If that’s the case, he added in his regular voice, “that’s wonderful.”

As for Mr. Mamdani, Mr. Salam doesn’t believe they have ever been in the same room, and isn’t sure they would have all that much to talk about. “He seems to have a rather well-developed theory about the world,” he said.

This is also something one could say about Mr. Salam. He holds an admittedly idealized memory of his own childhood, in Borough Park, during the Giuliani years. His parents worked long hours and saved enough money to eventually buy a small home in nearby Kensington. They rented out the top floors, and the family slept in a partially finished basement, until they saved enough money to take over the whole house.

Mr. Salam now makes about $800,000 a year from his post at the institute and lives with his own family in a home in a nearby neighborhood. The story of his family’s rise from one generation to the next is part of why he sees New York as the ultimate beacon of ambition, prosperity and capitalism.

His current neighbors in a leafy, low-slung part of the city close to Prospect Park are perfectly lovely, he said. Many of them have more than his parents did when he was a child: social and cultural capital, and at least some family money. And yet they seem to feel the city owes them even more, he said, in the form of free child care or buses or cheaper groceries.

Even if he can’t convince them otherwise, there may be something else that will: Mr. Mamdani failing to deliver all he has promised. He sees it as inevitable.

“Someone is going to have to pick up the pieces,” Mr. Salam said. “And I think that’s going to be our responsibility.”