What would Sen. John McCain want to teach Stephen Colbert if the comedian becomes the next senator from South Carolina? "How to shut up," the Arizona Republican told reporters with a chuckle on Tuesday.

A new poll from Public Policy Polling suggests that Colbert leads the field of potential candidates to fill the seat being vacated by Republican Sen. Jim DeMint. DeMint shocked Washington last week by announcing he was resigning to head the conservative Heritage Foundation think tank.

Asked what sort of senator Colbert would be, McCain deadpanned, "He would be a very valued member, in many respects, in that he seems to know everything about us, so he wouldn't have any trouble fitting in."

What's the very first thing you would teach him?

"How to shut up," the senator said, punctuating the joke with a little laugh.McCain was also asked who would be funnier, Colbert or "Saturday Night Live" alumnus Al Franken, now a senator from Minnesota? (Or McCain himself, suggested one reporter, apparently quite taken with the former presidential hopeful's acerbic sense of humor.)

"You'd have to leave that to others to judge," McCain demurred.