“Never take sides against the family” — that’s the creed of the Corleone family in “The Godfather,” and the Democratic Party today.

And Sen. John Fetterman is their Fredo.

Not because of incompetence on his part, but Fetterman is being blasted for betraying the “family” by his collegiality with President Trump.

Fetterman has broken with his party on some policy issues and was the first Senate Democrat to meet with Trump after he was elected, despite slamming him on the campaign trail.

“I haven’t changed my core values throughout out all this,” the Pennsylvania senator told KDKA-AM radio in Pittsburgh. But, he said, engaging with Republicans is “one of the reasons why they elected me, they wanted me to do these things.”

“Engaging with Republicans” is Democratic heresy these days. And Dems are working overtime to take Fetterman down.

The same party that rallied behind Fetterman after his stroke in 2022 is now questioning his mental fitness. The irony that Dem leaders looked the other way as former President Joe Biden showed signs of cognitive decline until they couldn’t hide what the rest of us saw is stunning.

But this is politics, and head-smacking hypocrisy is par for the course.

Back in January, Christine Jacobs, who founded Represent PA, an organization to help elect Democratic women to Pennsylvania’s legislature, told the Associated Press the Democrats she was talking to were both disappointed and concerned by Fetterman’s dalliance with Trump.

Their worry, Jacobs said, is that “Trump can say he’s talking to Democrats like John Fetterman, but it’s not going to change what he does and it’ll end up looking like John Fetterman’s being used.”

Those are the only two reasons a Democrat could be talking to Trump — mental issues or they’re being used as a pawn.

The latest salvo against the senator is an article in left-leaning New York magazine, which reported concerns from some of his current and former staffers over his mental state.

“It’s a one-source story with a couple of anonymous sources, a hit piece from a very left publication,” Fetterman told NBC News.

But the hit was a success among Democrats.

“He needs to resign,” The Bulwark’s Jonathan Last said on The Secret Podcast with co-host Sarah Longwell.

Longwell agreed and called the piece’s revelations “career-ending.”

If there’s any comfort for Fetterman, it’s that he’s not alone.

Michigan Gov. Gretchen Whitmer dared to defy the party line last month, first meeting with Trump in the Oval Office, then giving the president a hug when he arrived in her state, and later appearing at a press conference with Trump at Selfridge Air National Guard Base as he announced new fighter jets for the base.

“My job is to do the right thing for the people of Michigan,” she told The Associated Press after her appearance with Trump. “I’m not thinking about anything beyond that, and I know it’s hard for people to get their head around.”

Very hard. Sunny Hostin, co-host of The View said of Whitmer, “she just got used and played.”

A Reddit post from the political group 50501 accused her of “destructive enabling behavior.”

Fetterman and Whitmer dared to take sides against the family. The chance that Americans can be represented by lawmakers who put their needs above the party line? We’re afraid that kind of plot twist only happens in Hollywood.