STOCKTON, Calif. — Michael R. Bloomberg and Mayor Michael Tubbs of Stockton seemed like an improbable political duo on Wednesday as they heaped praise on each other. Mr. Tubbs, a 29-year-old liberal who is Stockton’s first black mayor, hailed Mr. Bloomberg as a leader “with the resources, with the record and with the relationships” to defeat President Trump in 2020. Mr. Bloomberg, a 77-year-old centrist billionaire, called the younger man “my kind of mayor.”
Mr. Tubbs had reason to feel kinship with Mr. Bloomberg. Last year, he graduated from a mayoral training program that Mr. Bloomberg sponsors at Harvard University. Mr. Tubbs had attended a conference co-sponsored by Mr. Bloomberg’s philanthropic foundation in Paris in 2017, and was featured in its 2018 annual report. And this past June, Mr. Bloomberg’s foundation donated $500,000 to an education reform group based in Stockton, a struggling inland city in Northern California.
As Mr. Bloomberg traverses the country as a presidential candidate, he is drawing on a vast network of city leaders whom he has funded as a philanthropist or advised as an elder statesman of municipal politics. Bloomberg Philanthropies, which has assets totaling $9 billion, has supported 196 different cities with grants, technical assistance and education programs worth a combined $350 million. Now, leaders in some of those cities are forming the spine of Mr. Bloomberg’s campaign: He has been endorsed so far by eight mayors — from larger cities like San Jose, Calif., and Louisville, Ky., and smaller ones like Gary, Ind., representing a total of more than 2.6 million Americans.
For all of those endorsers, Mr. Bloomberg has been an important benefactor. All have attended his prestigious boot camp at Harvard that gives the mayors access to ongoing strategic advice from Bloomberg-funded experts. More than half have received funding in the form of grants and other support packages from Mr. Bloomberg worth a total of nearly $10 million, according to a review of tax documents and interviews with all eight mayors.
The money he has given to cities underscores the extraordinary nature of Mr. Bloomberg’s candidacy. More than any presidential candidate in recent history, Mr. Bloomberg has established himself — through philanthropic giving, political endorsements and campaign spending — as a singular ally for a large cross-section of American politicians, many of whom feel a deep sense of loyalty in return. And there is no group to whom he is more tightly bonded with than his fellow mayors.
Who’s in, who’s out and who’s still thinking.
Mayor Steve Benjamin of Columbia, S.C., a co-chairman of the Bloomberg campaign, said Mr. Bloomberg’s philanthropy had earned him trust and consideration from mayors.
“It’s given him a great, great deal of credibility with people who, but for his philanthropy or altruism, he never would have interfaced with,” Mr. Benjamin said.
That credibility could be particularly important in the 2020 presidential race, which Mr. Bloomberg entered late last month. After an onslaught of self-funded television ads, he reached 5 percent support in two national polls this week.
Mayors have historically played an influential role in Democratic primary politics, lending their local political organizations to national candidates. And as a former Republican with relatively conservative views on business regulation and law enforcement, Mr. Bloomberg has been eager to demonstrate that mayors and other hands-on leaders in the party, particularly black elected officials, are willing to embrace his candidacy.
His decision last month to apologize for stop-and-frisk policing in New York was informed by feedback from these officials, people familiar with Mr. Bloomberg’s conversations said.
In Stockton, that shift helped earn Mr. Bloomberg a forceful ally in Mr. Tubbs, who this week invoked his own identity as a young black man with an incarcerated parent to vouch for Mr. Bloomberg. He said that Mr. Bloomberg’s willingness to use his wealth for public purposes was a strength in the race, pointing to his extensive spending for Democrats in the 2018 elections.
The Stockton mayor said he had urged Mr. Bloomberg to support voter-registration and voting-rights groups, including Fair Fight, the national organization led by Stacey Abrams. Ms. Abrams’s aides were also appealing to Mr. Bloomberg: He has committed to donating $5 million to Fair Fight, according to an Abrams adviser.
“Lots of people have money,” Mr. Tubbs said. “But the way he uses his money speaks to how he’s someone who has a vision for this party.”
Mr. Tubbs and other mayors say they are endorsing Mr. Bloomberg because of his platform and ideas, not because of any pressure, but some acknowledged that his wealth and philanthropy were an unavoidable factor.
Mayor Svante Myrick of Ithaca, N.Y., a city of about 31,000 that won a $100,000 Bloomberg grant for a supervised injection facility, said Mr. Bloomberg’s campaign had swiftly reached out after he entered the race to seek support. Mr. Myrick, who has not endorsed a candidate, said it had not occurred to him to weigh Mr. Bloomberg’s foundation in his thinking.
“Maybe I should be thinking about: If I endorse Bloomberg, Bloomberg Philanthropies will give us more money,” he mused.
Mr. Bloomberg is one of the richest people in the world, with a net worth estimated at more than $50 billion. While other politicians often donate small sums to their allies, the breadth and depth of his giving thus far — and the possibility of it in the future — is unmatched in scale.
“When you’re that wealthy you can spread your munificence anywhere that matters,” said Rob Reich, a co-director of the Center on Philanthropy and Civil Society at Stanford. “You acquire at a minimum a reserve of good will and more realistically a background capacity for influence.”
Stu Loeser, a Bloomberg spokesman, said that the former mayor was “damn proud” of the work supporting mayors and cities. “Unlike Donald Trump, Mike Bloomberg has a real foundation that does real work addressing people’s serious needs with no expectations of anything in return,” Mr. Loeser said.
Mr. Bloomberg and his allies acknowledge that they hope his connections to city leaders will be helpful in the presidential race. This month, at a meeting of the Texas Democratic Party’s executive committee, Mr. Bloomberg noted that he had “worked with, and my foundation has supported, a variety of mayors across the state,” including Julián Castro, the former mayor of San Antonio and presidential candidate.
Many mayors need no reminding of Mr. Bloomberg’s presence in their areas.
As the mayor of Huntington, W.Va., Steve Williams was not sure initially what to make of Mr. Bloomberg. “I thought he was going to tell me what kind of sugary drinks I could drink and not drink, would shut down the coal mines and tell us whether or not we could own guns and go hunting,” he said, referring to some of Mr. Bloomberg’s priorities and past initiatives.
Like other mayors in the Bloomberg orbit, Mr. Williams has been involved with numerous programs sponsored by Bloomberg Philanthropies, on everything from tackling an obesity epidemic to a love-your-block neighborhood program. The Appalachian city won a $1 million grant to create a wellness program for emergency medical workers.
Victoria Woodards, the mayor of Tacoma, Wash., attended the Harvard program and two CityLab conferences, gatherings focused on urban issues co-sponsored by Bloomberg Philanthropies. At the most recent one in Washington, she sat next to Mr. Bloomberg at a dinner at the National Museum of African American History and Culture.
At a city summit in San Antonio last month she had coffee with James Anderson, formerly the head of government innovation at the Bloomberg foundation. He told her that Mr. Bloomberg had jumped into the presidential race and asked her to join their team; she did weeks later, after her first choice, Senator Kamala Harris, dropped out.
Mayor Greg Fischer of Louisville began working with Mr. Bloomberg’s team within a few months of taking office in 2011, and his city received about $4.7 million in grants during his first three years in office. Now, Mr. Fischer is helping lead Mr. Bloomberg’s outreach to other mayors struggling with their budgets.
“Most city governments — I can tell you ours is — we are super-strapped for financial resources,” Mr. Fischer said. “It’s competitive and so it’s hard to build the relationships and win these things and when we do we celebrate around here.”
Now, some of the same people who aided these mayors from Mr. Bloomberg’s foundation are the ones asking for their political support. Mr. Anderson, who several mayors described as the most vital point of contact at Bloomberg Philanthropies, is now directing the campaign’s “Mayors for Mike” coalition. He and Patricia E. Harris, the foundation’s longtime chief executive, have both moved over to the campaign, changing email addresses and phone numbers but not their relationships with mayors and other leaders.
Mr. Williams, the Huntington mayor, recalled a phone call from Mr. Anderson, “wanting to have a separate conversation from the foundation, asking, ‘Can we switch gears?’” he said.
“He has a separate telephone number from where it was before. He emails me to my personal email address. It’s always very clear. Personal number. Campaign number,” Mr. Williams said. “They understand the lines of demarcation.”
Mayor Lori Lightfoot of Chicago, a current participant in the Bloomberg Harvard program, said that Mr. Bloomberg’s foundation was “deeply entrenched in Chicago” and that she and her staff had discussed how to keep its work separate from her political considerations.
“We view them as valued partners but that’s got to be separate and apart from any presidential considerations,” said Ms. Lightfoot, who has not endorsed any candidate in the Democratic race.
But Mr. Reich, the Stanford expert, was skeptical about the effect of logistical steps like separating email addresses. “It’s a detail that seems to miss the point of the exercise, which is to erect a wall between the activities of a philanthropist and the political interests of the donor,” he said.
Mr. Anderson, in an email, said local leaders were supporting Mr. Bloomberg because of his record of work helping communities.
“We’ve been working very hard to make our case to each and every mayor — nothing expected, nothing owed,” he said.
So far, only a few of the mayors linked to Mr. Bloomberg’s foundation have actually endorsed his campaign. In most of the country’s biggest cities, mayors have remained neutral in the presidential race; the most prominent city executive to take a side, Jim Kenney of Philadelphia, endorsed Senator Elizabeth Warren of Massachusetts. (Mr. Bloomberg spent $1 million on Mr. Kenney’s re-election earlier this year.)
One graduate of the Bloomberg program at Harvard is a leading opponent in the presidential race — Mayor Pete Buttigieg of South Bend, Ind., whose city also received $1 million from a Bloomberg program in 2018.
Every week in Mr. Bloomberg’s late-starting campaign has showcased, in one way or another, his donations to cities and the mayoral alliances he has created.
One of Mr. Bloomberg’s first campaign events was in Jackson, Miss., where he appeared with Chokwe Lumumba, the city’s 36-year-old mayor. A progressive Democrat who hosted Mr. Bloomberg but did not endorse him, Mr. Lumumba also attended the Harvard program and received from Bloomberg Philanthropies a $1 million grant to his city as a winner of the Public Art Challenge.
“It’s up to the leaders negotiating those things to be disciplined and principled enough that their decision-making isn’t unduly swayed,” Mr. Lumumba said.
Earlier this month, Mr. Bloomberg flew to Augusta, Ga., to announce the endorsement of the city’s mayor, Hardie Davis Jr., who had graduated from the Harvard program and had traveled to a CityLab conference in London where he met with Mr. Bloomberg. And his city received support from a Bloomberg program, What Works Cities, that deployed experts to Augusta for six months.
“You can’t put a price on that,” Mr. Davis said.
As for the training program outside Boston, Mr. Davis quipped, “As a proud Georgia Tech graduate, it doesn’t hurt to have this Harvard Bloomberg Institute certificate to go with that.”
Before his visit to Stockton, Mr. Bloomberg announced he had also won the endorsement of Mayor Sam Liccardo of San Jose, Calif., who had previously supported Ms. Harris. San Jose won a substantial award through Mr. Bloomberg’s American Cities Climate Challenge — a package worth about $2.5 million, a city spokeswoman said. Mr. Liccardo said there had been “no string attached” to any of the money.
Ms. Woodards, the Tacoma mayor, described an enduring connection for city leaders inducted into Mr. Bloomberg’s network.
“When you start to engage with Mike,” she said, “you are with Mike forever.”
Astead W. Herndon contributed reporting and Kitty Bennett contributed research.