02/16/2012 02:54 am ET Updated Apr 16, 2012

Jon Stewart's Joke Hits A Little Too Close To Home On 'Late Show With David Letterman' (VIDEO)

Jon Stewart is a funny guy, and he's usually pretty quick-witted as well. On "Late Show" (Weeknights, 11:35 p.m. EST on CBS), he saw an opportunity for an off-the-cuff riff and went for it. Unfortunately for him and the increasingly uncomfortable David Letterman, that joke hit a little close to home for the host.

Stewart saw the opening after Letterman commented that Mitt Romney reminds him of the guys on the packaging for men's underwear.

"I would think at this stage of your career, you have people that could just sit there and hug your groin for you," he told Letterman. "Just hold on. Just do that. You could have like a group of people --" At this point, he started losing his focus, later admitting that he'd realized his faux pas mid-joke.

"Jon, Jon, Jon," Letterman said calmly. "I had a little trouble along those lines." He was referring to the revelations in 2009 that he'd had intimate relations with female members of his staff, including with a woman who was at the time his personal assistant.

Stewart said that while he'd realized what he'd just done, he was too far in -- too committed to the joke -- to pull back. Letterman laughed it off, but it certainly looked like Stewart wasn't ready to stop apologizing just yet.

Jon Stewart can be seen weeknights on "The Daily Show" weeknights at 11 p.m. EST on Comedy Central, while David Letterman hosts "Late Show" weeknights at 11:35 p.m. EST on CBS.

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