But despite his recent surge in polls, that might be a difficult task, as he remains a divisive figure among a group historically important to Democrats — labor unions.
To be sure, unions' support or opposition may not make or break Democratic candidacies this cycle, as key constituencies within the party are merely looking for the best chance to win in November. The influential Nevada Culinary Workers' union declined to support any of the Democratic candidates ahead of the debate Wednesday night and the state's caucuses this Saturday. Nor is there a clear front-runner for endorsement of the 12.5 million-member AFL-CIO, as former Vice President Joe Biden, once the would-be union darling, continues to fall in the polls.
Yet the chances of Bloomberg becoming a champion of organized labor early in the primary season might seem small, despite his recent unveiling of some union-friendly policy proposals. Bloomberg's media company, Bloomberg LP, is not unionized, though the legal research firm it acquired in 2011, Bloomberg BNA, does have a union.
During his three-term run as New York mayor, Bloomberg's tough tactics earned him a mixed record with unions: He had his share of enemies and allies, as well as people who straddled the divide.
As the city's finances took a hit from an economic crisis and a ballooning deficit, Bloomberg targeted union contracts and pensions as a path to financial stabilization. He ended his 12-year run on Dec. 31, 2013, with a balanced budget. But he had lost the support of New York's largest municipal public employee union, District Council 37, which had backed his first run. The union represents workers in hospitals, schools libraries and city colleges.
Other union criticisms of Bloomberg persist. Patrick Lynch, the president of the Police Benevolent Association, which represents 24,000 sworn New York Police Department members, has called Bloomberg's apologies for stop-and-frisk "too little, too late." The union has said Bloomberg's policy worsened its relations with communities and made police officers the target of hatred.
Bloomberg has also drawn anger from the teachers unions for his support of charter schools, which the groups say drain public schools and educators of resources. After Bloomberg announced his run for president late last year, the United Federation of Teachers declared in a newspaper distributed to its more than 190,000 members that under his watch in New York "public school educators felt disrespected and demoralized" while "students were shortchanged."
His charitable activities as a private citizen have proven equally as divisive. Through Bloomberg Philanthropies, he's continued to support private education, as well as a coal-free future, both controversial decisions for certain union members. Those same activities, though, have also earned him allies.
Despite the teachers union's past issues with Bloomberg, the president of its parent union, the 1.7 million-member American Federation of Teachers, Randi Weingarten, recently told the Hill she believes Bloomberg has a chance of "going all the way." Bloomberg Philanthropies has pledged money to support low-income students. The AFT, meantime, has partnered with Everytown for Gun Safety, the gun-safety advocacy group that Bloomberg helped found.
Weingarten and Bloomberg shared a byline in a USA Today editorial in 2018 acknowledging that while they have butted heads over the best way to improve schools, they share a focus on fair pay for teachers.
The country's largest federation of unions, the AFL-CIO, is also split on Bloomberg, a person familiar with the union's thinking said, requesting anonymity in order to speak freely about union dynamics.
There are others, though, who are in favor of Bloomberg's candor and frank approach. Some are focused on simply finding a candidate they think can win.
"I've certainly seen people express concerns about Bloomberg," said Thea Mei Lee, president of the Economic Policy Institute, who previously served as deputy chief of staff at the AFL-CIO. "But they're also trying to figure out who can beat Trump, and having money is always useful in the election."
The Bloomberg campaign did not respond to a request for comment for this article.
The Democratic field is as fractured as the union voter bloc.
Sen. Bernie Sanders, I-Vt., an outspoken proponent of organized labor, has already irked some unions with his support for "Medicare for All" and his opposition to mountaintop coal mining. Biden, who has pegged much of his political appeal to his blue-collar roots, failed to secure the endorsement of the influential Nevada Culinary Workers' union ahead of the state's caucuses.
The other major Democratic candidates — Sen. Elizabeth Warren, D-Mass., former South Bend, Indiana, Mayor Pete Buttigieg and Sen. Amy Klobuchar, D-Minn. — all have various levels of support among union members. But none have been able to break free as the clear front-runner nor allayed sufficient concern they can beat Trump.
Trump, a Republican billionaire, nonetheless won the presidency in 2016 by winning over large swaths of union members and blue-collar workers. That happened despite his rival, Hillary Clinton, winning the endorsement of the AFL-CIO.
Meanwhile, dwindling union membership and economic uncertainty have created schisms between unions representing workers from industries such as mining, teaching and retail. That fracture was made clear with the recent United States-Mexico-Canada Agreement, a NAFTA update that earned the support of the AFL-CIO, despite concerns several unions publicly expressed about the deal.
The AFL-CIO's endorsement doesn't seem to have the impact it used to have. In 2016, the organization endorsed Hillary Clinton, but she only beat Trump among union households 51%-43%. In 2012, Barack Obama beat Mitt Romney among union households 58%-40%.
It's also unclear whether the AFL-CIO will arrive at a two-thirds majority vote required for the group to endorse any candidate, the person familiar with the AFL-CIO's thinking acknowledged. The AFL-CIO's member unions include the United Food and Commercial Workers International Union, International Association of Machinists and Aerospace Workers, and United Auto Workers.
The AFL-CIO has only once before opted against any endorsement at all. In 1972, it refrained from endorsing either President Richard Nixon or Democratic Sen. George McGovern for the presidency, put off by McGovern's opposition to the Vietnam War.
Tim Schlittner, a spokesperson for the AFL-CIO, said the group is "fully confident" in its ability to reach a consensus to support a candidate as it works through a "strong field." Schlittner also disagreed that the AFL-CIO is fractured or losing influence, calling such characterizations "overblown," and saying it "comes together like a family" when it needs to.
Given Bloomberg's $60 billion net worth and his extensive support network, he might be able to run a strong campaign without the biggest union's endorsement in the primary or in the general election. He has already shelled out $400 million on ads. The former New York mayor is polling in third place nationally among Democrats, within striking distance of Biden, after starting in seventh place when he jumped into the race, according to a Real Clear Politics polling average. Sanders is the leader.
Unions' strongest weapon in elections is their ability to canvas and rally voters, yet Bloomberg has put together a towering campaign operation that has broken records with its ad spending and promotion, as well as an army of operatives. Meantime, through his private philanthropy, he has built up a network of mayors that has brought in scores of endorsements in swing states such as Pennsylvania and North Carolina.
He is also rolling out policies that seem more union-friendly than his track record in New York would suggest, even as the U.S. stares down a $1 trillion deficit.
This weekend, he unveiled a plan that would raise the federal minimum wage, strengthen union protections and "protect workers' pensions." It marks a contrast from his time as mayor. Then, he argued that a right to unionize must be met with a reduction in union pension and benefit costs.
His plan to rein in Wall Street, released Tuesday, proposed tougher regulation on banks despite his previous criticism of bank regulation imposed under the Dodd-Frank Act.
A K-12 education plan — which will likely address the question of school privatization — will be released in the next few weeks, a campaign spokesperson told CNBC.
These proposals show, for all of his wealth and firepower, that Bloomberg might think he could use a little union muscle to help him win it all, if he clinches the nomination.
"He certainly has a considerable buffer as a result of the resources he has, but a buffer and a complete insulation are two very different things," said Harley Shaiken, a labor economist at the University of California at Berkeley. "Unions know how to organize, they can take phone calls — and in an internet age and an age of limited TV ads, there's still something to that."