Mike Bloomberg is mulling another run for president — but as a Democrat, sources close to the former three-term mayor said.

If he takes the plunge, Bloomberg would be 78 when he’s competing in Democratic primaries across the nation.

Last week, he said he would pump $80 million of his vast personal fortune to aid Democrats in the congressional midterm elections this year.

“That’s an indication of where his head is at,” a Bloomberg insider said Tuesday.

Bloomberg himself hinted at his thinking on June 6, when he was honored at a YMCA fundraiser at Cipriani 42nd Street.

At the end of his speech Bloomberg told the 500 guests, “Before you leave I want to get your cellphone number because I’m thinking of getting the band back together,” said one source.

The well-heeled attendees erupted into thunderous applause, believing Bloomberg was telegraphing his interest in taking on President Donald Trump.

Bloomberg, 76, considered making a bid for the presidency in 2016 as an independent. But he ultimately decided not to run, concluding that he could not win on a third-party line.

Bloomberg endorsed Democrat Hillary Clinton in 2016, even delivering a prime-time speech at the Democratic National Convention trashing Trump.

Although elected on the Republican line, Bloomberg is closer to Democrats on key issues — gun control, taxes, infrastructure and climate change.

Bloomberg did not mince words on what he thought of Trump in his DNC speech two years ago.

“Throughout his career, Trump has left behind a well-documented record of bankruptcies, thousands of lawsuits, angry shareholders, and contractors who feel cheated, and disillusioned customers who feel ripped off. Trump says he wants to run the nation like he’s run his business. God help us. I’m a New Yorker, and New Yorkers know a con when we see one,” he said.

But Trump got the last laugh — he won.