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BURBANK, Calif. (AP) - On Jay Leno's "Tonight Show," Republican presidential front-runner Mitt Romney was mostly business - though he slipped in a few jokes at the expense of his host and his main political opponent.

Romney cracked Tuesday night that he'd pick Leno rival David Letterman as his vice president, talked at length about health policy and said he'd be happy to have a rival of his own, Rick Santorum, serve in a Romney administration.

And when he was asked to pick just a word or two to describe potential running mates, Romney had choice words for Santorum: "Press secretary."

The jab played off the former Pennsylvania senator's recent run-in with a New York Times reporter. Santorum had cursed at the reporter, accusing him of misinterpreting some of his remarks.