Stephen Colbert to Rand Paul: 'You tried to sell me pot backstage!'
Sen. Rand Paul (CBS)

It's no secret that Sen. Rand Paul (R-KY) thinks Donald Trump is a joke -- but he wants to remind voters that the Republican frontrunner is dangerously unsuited to serve as president.

The Kentucky Republican appeared Wednesday on "The Late Show With Stephen Colbert," where he traded jokes about his hair and wardrobe before turning serious in an answer about his GOP rivals.

"All kidding aside, I think there's a certain seriousness to leading a nation of 300 million," Paul said. "I guess what concerns me is, in the last debate, there was a discussion of the nuclear triad -- that means we have missiles by air and by land and by sea."

"But the thing is, he seemed to be unaware that we even had that, but then a week later it's even scarier," Paul continued. "Mr. Trump says, 'Of course, we've got a nuclear triad, and our biggest problem is that we've been unwilling to use it enough.' We're kind of making light, but that shouldn't be made light of."

Colbert said he admired Paul and his father, former presidential candidate and Rep. Ron Paul, for staking out positions that strayed from partisan orthodoxy.

"He's almost libertarian, I'm libertarian-ish," Paul explained. "In sort of general terms, Republicans haven't been very good with your personal privacy or your personal liberty, but Democrats haven't been very good with your economic liberty -- they want all kinds of rules on business that interfere with the marketplace. Government on the Republican side wants to collect your phone records, be involved in what you do in your home. Libertarians say, you know what? We want to leave you the hell alone, no matter what -- whether it's your business or your private life."

Colbert asked if he had anything in common with Sen. Bernie Sanders, who is mounting an enthusiastic challenge to Clinton.

"Yeah, we work in the same place," Paul said.

Paul said he frequently worked with Sen. Ron Wyden (D-OR) on NSA and foreign policy reforms, including bringing troops home from Afghanistan -- and Colbert asked him about drug policy reform.

"You're not going to ask about pot, are you?" Paul said.

"Are you a cop? Because if you're a cop, you have to tell me you're a cop or this is entrapment," Colbert said, as Paul jokingly mopped his brow.

"I thought we said before we would not talk about pot, Stephen," Paul said.

"You tried to sell me pot backstage," Colbert said. "I'm sorry -- you tried to sell me on the idea of changing sentencing guidelines for pot. I should have said the entire sentence, I apologize."

Watch the entire interview posted online by The Late Show With Stephen Colbert: