Comedy Central's Jon Stewart explained to CBS host David Letterman on Wednesday that Republican presidential candidate Mitt Romney's problem was that at close examination, he was just "pixels" instead of a real person.

"The guy I feel worse for is Romney," Stewart remarked.

"Mitt?" Letterman asked.

"Not just for that," Stewart joked. "Because he's the guy, you know, who considers himself next in line. The guy at the deli who's like, 'But I'm number six.' But they don't like him, the voters. Because he wants to be a regular guy but he can't be himself. He puts on jeans but you know he's got a suit and pants underneath. He's trying to be like, 'I'm a regular guy.' But he's always got like tells. He's in a bar and he's like, 'Sure, I used to hang out in this bar. Give me one of those malted-hops drinks.' Nothing is authentic."

"I realize Rick Santorum is the guy Mitt Romney is pretending to be," he added. "There's a certain inauthentic quality."

"I know nothing about politics," Letterman noted. "But as the president, you want a guy who makes good decisions. Putting your dog on the roof of your car and driving to Toronto is not a good idea. I don't want -- that's it, end of story. I don't care about anything else."

"If you were to open a box, if you were to design something to be a president, that's what you would make it look like," Stewart said of Romney. "It's sort of like when you see those Pixar movies. What is it? Tintin -- 'The Adventures of Tintin.' You look at it and you go, 'Oh, is that real dog?' But then you look closer and you go, 'Oh, no. That's just an avatar.' You know what I mean? That's when you look at Romney, he's like pixels. I think if you look at him closely, it's zeroes and ones."

"He reminds me of the guy you see on the package of underpants," Letterman agreed.

"Do you even have to wear underpants anymore?" Stewart asked. "I would think at this stage of your career, you just have people who can sit there and hug your groin for you. Just hold on. You got like a group of people -- I'm sure, I got people who take a college credit for that."

"Jon, I had a little along those lines," Letterman pointed out, referring to sexual relationships he had with female staffers.

"Can I tell you something," Stewart admitted. "I'm half way through that bit and all the sudden I realized, 'What the fuck am I doing?'"

Watch this video from CBS's The Late Show, broadcast Feb. 15, 2012.

(H/T: Gawker)