Now that he’s no longer a candidate, multi-billionaire Mike Bloomberg is set to become former rival Joe Biden’s rich best friend.

Bloomberg could convert his massive campaign infrastructure into an independently-run pro-Biden or anti-Trump Super PAC — as long he doesn’t coordinate with any presidential campaign, a spokesman for the Federal Elections Commission said.

Bloomberg on Wednesday ended his presidential bid and endorsed Biden, the former vice president.

Bloomberg — worth $65 billion –could dump hundreds of millions of dollars into the Super PAC to pay for ads, hire staff to knock on doors and even repurpose his campaign offices across the country — to promote Biden or slam Trump.

The Bloomberg campaign has 2,400 paid staff — including 2,000 in 43 states and territories another 400 at its Times Square headquarters. Any or all of them can be used to aid Biden’s bid independent of his campaign.

“We have a massive, built-in campaign infrastructure. If you’re Joe Biden you don’t have to build it,” said one Bloomberg campaign insider. “This has never happened before in the history of the Republic.”

The primary contest for the Democratic nomination for president has now become a two-way race between Biden and Vermont Sen. Bernie Sanders. Bloomberg has warned that Trump would win re-election and the Democrats would lose the House majority if Sanders, a democratic socialist, becomes the nominee.

It was unclear Wednesday whether Bloomberg would use his resources to unload on Sanders to aid Biden in the primary race.

Bloomberg campaign manager Kevin Sheekey vowed in January that the former, three-term New York City mayor would be the most crucial backer in the effort to beat Trump if he wasn’t the candidate himself.

“Mike Bloomberg is either going to be the nominee or the most important person supporting the Democratic nominee for president,” Sheekey said. “He is dedicated to getting Trump out of the White House.”

Hawkfish, the Bloomberg-founded digital company behind his social media ads would be retained through Election Day, campaign officials have said.

Sheekey, in a conference call on Wednesday, told campaign staffers that Bloomberg was putting his muscle behind Biden. But decisions about how many campaign staffers would be retained was yet to determined, and more would be known in the next seven to ten days, sources said.

Independently-run fundraising arms — SUPER PACS bankrolled by millionaires and billionaires — have played a role in modern presidential politics.

The pro-Obama Super PAC Priorities USA slashed opponent Mitt Romney in TV ads in 2012 as a heartless businessman whose businesses closed firms and put employees out of work.

President Trump’s wealthy backers help bankroll a stable of pro-Trump groups: Great America PAC, the Committee to Defend the President, America First Action PAC, Future 45 PAC and Rebuilding America PAC.

Pro-Trump forces are away ahead of the Democrats in the PAC spending war — but Bloomberg could level the playing field in a hurry – and Trump’s backers know it.

“Bloomberg could be the great equalizer. No one has spent money the way he has. He could fill a lot of air space,” said Ed Rollins, founder of the pro-Trump Great America PAC, which spent $35 million to aid Trump in 2016.

Rollins, who ran the late President Ronald Reagan’s re-election campaign in 1984, also said Bloomberg will try to “save face” after his $550 million presidential campaign flamed out.

Bloomberg could end up being more a force for Democrats as its financial booster than a candidate, said U. of Virginia professor Larry Sabato.

“Bloomberg is the only hope the Democrats have. The Trump Republicans have been preparing for this election for years, day in and day out,” Sabato said.

The billionaire philanthropist spent more than $110 million in 2018 through his already-established super PAC, Independence USA PAC, to help get Democrats elected in the House.