David Letterman is calling Donald Trump’s presidency an “experiment” that “didn’t work,” saying the commander in chief should step down.

“It’s time to go,” the longtime face of CBS’s “Late Show” said of Trump in a Wednesday interview on SiriusXM’s “The Howard Stern Show.”

“It was an experiment. We put an outsider in the office. Well, it hasn’t worked. Just resign,” Letterman, 70, said.

“The impeachment thing will take forever and may not end with a conviction,” Letterman continued.

{mosads}

“You just get together some people, like his sons, Don Jr. and Don Jr. Get those two guys together. Probably Regis [Philbin], put him on the panel. And Gary Busey. And his daughter, the youngest one, Trumpina,” Letterman quipped.

“And just go to him and have him sign some papers and just move him down to Mar-a-Lago. They’ll build a little Oval Office for him down there. ‘No, you’re still president, dad.’”

Letterman has been a fierce critic of Trump — who was once a frequent guest on his late-night show — since stepping down from his hosting duties in 2015.

“He could take a punch,” Letterman said of having Trump on the late-night couch. “But I didn’t know that he was a jerk. It turns out, he’s a jerk.

“The thing I’m tired of is people [saying,] ‘Oh, can you believe what he did?’ Yeah, we can believe what he did,” Letterman added. “He’s been doing it for two years now.”

If Trump were to resign, Letterman said, “We’ll take it a step at a time. We’ll see what happens after that. But for the time being, we’ve had enough.”