He’s Benedict Bill.

Democratic leaders are fuming after Mayor Bill de Blasio turned his back on mentor and megasupporter Hillary Clinton by not endorsing her presidential bid.

A party source told The Post on Monday that Hizzoner has rankled the top echelon so much that donors may pull support for him when he’s up for re-election.

“Some of Hillary’s biggest bundlers are like, ‘WTF?’ ” the source said.

A city Democratic insider said he fielded furious calls and texts from Clinton’s people all day Monday, the day after de Blasio sniffed on NBC’s “Meet the Press” that it was too early to endorse any candidate.

“I need to see any actual vision of where [candidates] want to go . . . We need to see the substance,’’ said de Blasio, who has landed political jobs thanks to Clinton and her husband, Bill, and even served as campaign manager during her 2000 Senate bid.

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A Clinton source scoffed: “He’s known her for, like, 20 years! He doesn’t know what her philosophy of government is?”

The Democratic insider added: “The Clinton people are really angry. They’re furious.”

In a closed-door fundraiser for de Blasio in 2013, Clinton called him “a partner who always had my back,’’ CNN reported.

The source blasted de Blasio as a puppet of progressives.

“He does everything the Working Families Party tells him. The Working Families Party is still not for Hillary,” the source said.

Former Public Advocate and Democratic mayoral candidate Mark Green questioned why de Blasio was holding Clinton to a higher standard than Gov. Andrew Cuomo — who got the mayor’s endorsement last year despite their clashes on taxes and other issues.

“Q for BdB: if you insist on prog vision pre-endorsement, how come u jumped on Cuomo bandwagon unquestioningly?” he tweeted.

Even Republican Westchester County Executive Rob Astorino was more upbeat about Clinton’s candidacy than de Blasio.

“Westchester is proud to have Secretary Clinton as a leading candidate for president,” he said.

Sources suggested de Blasio refused to endorse Clinton after her aides made it known they were mad that he was headed to Iowa to talk about income inequality this week — at the same time she’ll be in the state.

“He doesn’t want to be taken for granted,” a city party insider said.

Democratic National Committee member Rob Zimmerman ripped Hizzoner.

“It is a moral imperative for people who are leaders of the progressive movement to support her,” Zimmerman told The Post.

State Democratic chair and ex-Gov. David Paterson also rapped him.

“When you know someone is running for president, I would think you would have [your endorsement] resolved by the time it’s announced,” he told Fox’s “Good Day New York.”

But de Blasio had some allies.

“Today is not the day to discuss endorsements,’’ said City Council Speaker Melissa Mark-Viverito, who also declined to back Clinton.

US Rep. Hakeem Jeffries (D-Brooklyn) also defended the mayor and said he, too, is not ready to officially back Clinton.

“He’s the mayor of the City of New York,” Jeffries told The Post. “He represents the interests of more than 8 million people. Before diving into a presidential campaign, it’s reasonable that Mayor de Blasio would want to hear a clearer articulation of where Hillary Clinton stands on the issues important to large numbers of New Yorkers.”

Jeffries supported Obama in 2008 over Clinton and said he is waiting to hear whether Vice President Joe Biden, Cuomo or others may join the contest.

De Blasio refused questions at Monday’s Mets opener, where the Red Sox-loving mayor was booed by the crowd.

Additional reporting by Yoav Gonen, Reuven Fenton and Kate Sheehy