They don’t even take power for another two months, but impatient House Democrats — especially New York’s own Rep. Jerrold Nadler — already are busy plotting a series of endless investigations of the Trump administration.

Spurred by the ouster of Attorney General Jeff Sessions, three incoming House committee chairs fired off at least nine letters demanding administration officials preserve “all materials related to any investigations” by special counsel Robert Mueller.

On top of signing such letters as future head of the Judiciary Committee, Nadler was busy tweeting out his demands for “answers immediately as to the reasoning” behind Sessions’ removal.

Yet the answer is simple: President Trump lost confidence in Sessions when the AG recused himself from overseeing the probe of Trump’s 2016 campaign. Indeed, Session’s imminent post-election departure was openly predicted for months — the “reasoning” for it painfully obvious.

So much for Speaker-apparent Nancy Pelosi’s vow that we won’t see “any scattershot freelancing” when it comes to Democratic investigations.

Because that’s just the least of Jerry Nad­ler’s ankle-biting plans.

As The Federalist’s Mollie Hemingway reported, Nadler was on a DC-bound train Wednesday, loudly blabbing away on his cellphone about his bizarre plan to try to impeach Supreme Court Justice Brett Kavanaugh for alleged perjury.

“We will be holding people accountable,” Nadler is warning as his moment in the national spotlight finally arrives. And there’s no mistaking that moving to impeach Trump tops his list.

He and other Dems would do well to consider Senate GOP Leader Mitch McConnell’s advice. He warns that such aggressive investigating just might turn around and bite them where it hurts.

“I remember when we tried it in the late ’90s,” said McConnell. “We impeached President Clinton, and his numbers went up while ours went down and we underperformed in the national election.”

Republicans back then listened only to their fiercely anti-Clinton base and it backfired. Now Democrats face the same hyper-emotional demands from their base.

With people like Jerry Nadler leading the charge, don’t expect them to play it smart, either.