As thousands of restaurants, Midtown office towers and Broadway theaters lay empty last summer, leaders of New York’s business community decided enough was enough: They wrote a scathing letter expressing no confidence in Mayor Bill de Blasio, and intensified efforts to find someone of their liking to replace him.

They drafted Raymond J. McGuire, one of the longest-serving and highest-ranking Black executives on Wall Street, to run for mayor, and promised their assistance.

Now, three months after announcing his candidacy, that support has come: Mr. McGuire’s campaign will report this week that it has already raised just over $5 million. It was an unusually high sum for such a short period, approaching the fund-raising totals of established candidates like Scott M. Stringer, the city comptroller, and Eric Adams, the Brooklyn borough president.

The amount is likely to jolt the race, pushing Mr. McGuire to the forefront of the free-for-all Democratic primary contest, placing pressure on Mr. Adams and Mr. Stringer to keep pace, and damaging the hopes of the other dozen or so candidates still struggling to meet fund-raising minimums to qualify for public matching funds.

Mr. McGuire’s donor list reads like an index from corporate America, Wall Street, the entertainment industry and real estate. There are at least 20 billionaires on the list, including owners of sports teams and oil company chief executives. There’s old money dating back to the Ottoman Empire, and new money earned with the kings and queens of hip-hop culture.

While the support illustrates the potency of Mr. McGuire’s candidacy, the ties to big business may be anathema to many left-leaning Democratic voters in New York, a city where political pressure has torpedoed efforts to expand Industry City in Brooklyn, and discouraged Amazon from pursuing a headquarters in Queens.

Indeed, prominent Republican donors are among Mr. McGuire’s supporters, including Ken Langone, one of the founders of Home Depot, and his wife, Elaine, who each donated the maximum amount of $5,100. Kara Ross, a jewelry designer and the wife of Stephen Ross, a friend and fund-raiser of President Trump who founded Related Companies, also donated $5,100, according to campaign finance data shared with The New York Times.

Mr. McGuire also received large donations from James L. Dolan, a major Republican and Trump donor who owns the Knicks and Madison Square Garden; and Richard S. Fuld Jr., the last chief executive of Lehman Brothers, which declared the largest bankruptcy in United States history during the 2008 financial collapse, and his wife, Kathy.

Mr. McGuire, a former vice chairman at Citigroup, did not shy away from his support in the business community.

“New Yorkers of all walks of life have shown they believe in our movement to lead the greatest comeback this city has ever seen, and everyone will be a part of it, no matter your race or religion, ZIP code or bank account, ideology or orientation,” Mr. McGuire said in a statement this week.

Mr. McGuire raised so much money that it will actually benefit the candidates participating in the city’s matching funds program; when a candidate who is not participating in the program — Mr. McGuire is not — raises or spends more than half of the spending cap for program participants, the $7.3 million spending limit for primary candidates may be increased by 50 percent, according to Campaign Finance Board regulations. The change would push the primary spending limit to $10.9 million.

Mr. Adams, the Brooklyn borough president, and Mr. Stringer, the comptroller, are the only two candidates who have met the threshold for matching funds so far.

Mr. McGuire’s campaign has more than 3,700 donors who gave an average amount of $1,100. About 575 donors contributed the maximum amount. At least 75 percent of donors live in New York City, mostly in Manhattan.

Paul T. Schnell, a partner at the law firm Skadden, Arps, Slate, Meagher & Flom who oversees mergers and acquisitions, has known Mr. McGuire for 38 years and counts himself among the business leaders who nudged Mr. McGuire to run for mayor. Mr. Schnell and his family donated a total of $11,700 to Mr. McGuire. As the head of “Lawyers for Ray,” Mr. Schnell held a fund-raiser that raised more than $142,000, much of it from those who work at his law firm.

“He’s got a combination of leadership, management and business skills but also great people skills and empathy,” Mr. Schnell said. “He will use those skills to restore the city’s economy and he’s going to do that for small businesses as well as large employers.”

Mr. de Blasio has mostly avoided any relationships with business leaders, long priding himself on being a champion of the working class. When asked in December about equity in education, the mayor said that his “mission is to redistribute wealth.”

As the 2021 mayoral field began to take shape, it became clear that none of the presumed front-runners seemed interested in working with business leaders, and Mr. McGuire was strongly encouraged to enter the race.

A tipping point came last year, when the mayor was asked whether he worried that the wealthy were abandoning the city during the pandemic. The mayor responded, “We do not make decisions based on the wealthy few.”

The frustration in the business community has now translated into keen support for Mr. McGuire. He received donations from prominent business leaders such as William A. Ackman, chief executive of Pershing Square Capital Management; Danny Meyer of the Union Square Hospitality Group; Steve Stoute, a former record executive turned marketing executive; and Robert Reffkin, a co-founder and chief executive of the real estate brokerage Compass.

Hutham S. Olayan, a member of one of the wealthiest families in the Arab world, gave two donations of $2,500; there were 11 donations from members of the Tisch family and five donations from members of the Lauder family, including maximum donations from Leonard A. Lauder, the philanthropist and chairman emeritus of the Estée Lauder Companies, and his wife, Judy Glickman Lauder; his son William P. Lauder, executive chairman of the Estée Lauder Companies; and his niece Jane Lauder, who is also a high-ranking executive at the firm.

Voters are not likely to be surprised that Mr. McGuire, a Wall Street executive, would turn to wealthy friends to raise money, though progressives could make an issue of it, said Bruce Gyory, a Democratic strategist.

But with so many people vying for the Democratic nomination, including several progressive-minded candidates, it is not clear how much Mr. McGuire’s business ties will damage his chances, especially with ranked-choice voting allowing as many as five candidates to be chosen.

Mr. Gyory said that Mr. McGuire’s credibility in the business world could shore up support among Black voters.

“The question is can he take his fund-raising prowess and turn it into support in the Black community in Southeast Queens and the North Shore of Staten Island and create a message that resonates,” Mr. Gyory said. “African-American voters may say, we have a candidate who can compete and we should take a second look.”

Mr. McGuire also leaned on his personal business connections. Charles Phillips, Mr. McGuire’s campaign co-chairman and the former president of Oracle who sits on several corporate boards, and William M. Lewis Jr., co-chairman of investment banking at Lazard, are both personal friends. They co-hosted the initial fund-raiser for the campaign, which raised more than $400,000. Both also made maximum contributions.

Several well-known people in the entertainment industry also donated money to Mr. McGuire, including the filmmaker Spike Lee and his wife, the producer Tonya Lee Lewis; Mr. Lee provided the narration for Mr. McGuire’s campaign launch video.

Others included Michael Ovitz, co-founder of Creative Artists Agency; the ballerina Misty Copeland; Jessica Seinfeld, the cookbook author, philanthropist and wife of the comedian Jerry Seinfeld; Gwyneth Paltrow; Debra L. Lee, the former head of Black Entertainment Television; Valerie Jarrett, a former adviser to President Barack Obama; and the music executive Lyor Cohen.

The campaign has approximately $3.7 million on hand, which means that Mr. McGuire has been spending about $442,000 per month to keep his campaign staff of 25 running. By comparison, Mr. Stringer has $5.7 million on hand and has spent just over $429,000. Mr. Adams has $6.6 million on hand and has spent just over $367,000, according to the most recent campaign finance filings.

Carlos Menchaca, a councilman from Brooklyn, is one of the mayoral candidates who is not expected to reach the threshold for public matching funds. Mr. Menchaca, who was instrumental in turning back the proposed expansion and rezoning of Industry City, said that New York City is now committed to rejecting “candidates connected to toxic policy around development and Wall Street.”

“I’m incredibly confident that New Yorkers will see through these campaigns that have not distanced themselves,” he said. “Viability is not connected to money.”