The first ad out of the Colbert SuperPAC is harsh: It calls Mitt Romney a "serial killer." The one-minute spot, unveiled today, really is running in South Carolina, in a small ad buy that the PAC made in Charleston.

"As head of Bain Capital, he bought companies, carved them up and got rid of what he couldn't use," the narrator, John Lithgow, says in the spot.

Stephen Colbert announced the formation of an exploratory committee, but he immediately handed over the control of his SuperPAC to Jon Stewart because of prohibitions on candidates from coordinating with the independent expenditure groups that support them.

Colbert reinforced the point on ABC's "This Week" this morning, claiming that despite the viciousness of the attack on Romney, he has no control over the SuperPAC's activities. In fact, He claimed to barely even know Stewart.

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