Watch Howard Stern’s full one-on-one interview with Anderson Cooper in an hour-long “AC360” special event airing Friday at 10 p.m. ET on CNN.

CNN  — 

Radio shock jock Howard Stern believes President Donald Trump’s candidacy for president started out as a “publicity stunt” in order to get a raise from NBC for hosting “The Apprentice.”

Stern, who has hosted Trump on his radio show for years, told CNN’s Anderson Cooper in an interview set to air in full on Friday that he has “no doubt” it was a publicity stunt. Stern told Cooper that he has “inside information” that Trump started out using rumors that he would run for president as a public relations tactic when he was promoting his 1987 book, “The Art of the Deal.”

He said at first, it was a “PR guy’s idea. He said, ‘Donald, what you need to do is we’ll … make sort of a rumor that you’re running for president.’”

“So all of a sudden he was being interviewed,” Stern said. “The book goes right to No. 1.”

Stern said when Trump’s second book came out, “that’s when he decided to start the rumor that he was gonna run for president.”

For the 2016 presidential election, “‘The Apprentice’ ratings were – were not what they were. NBC was not gonna give (Trump) a raise. And what’s a better way than to get NBC’s interest? I’ll run for president, and I’ll get lots of press. And I think that’s what happened.”

Trump has appeared several times on Stern’s show “The Howard Stern Show,” where he has engaged in crude and demeaning conversations about women over many years.

Stern said Trump’s presidency is “unbelievable” to him and says he doesn’t think Trump likes being President.

Trump asked Stern if he would go to the Republican National Convention and endorse him in 2016, according to Stern.

Stern said “for about a split second, I went, can you imagine if I was all in? I would be the head of the (Federal Communications Commission). … I could be on the Supreme Court. I think Donald would give me anything I’d asked.”

He said he believes “100%” that “if Ben Carson can get in there” that Trump “would’ve appointed me to something.”