ABC NEWS: The harshest attack against Mitt Romney to yet hit the South Carolina airwaves is coming not from his GOP rivals, but from comedian Stephen Colbert , whose Super PAC is up with a 60-second spot accusing Romney of being a “serial killer.” The harshly-worded ad spares no drama, showing a butcher carving up a carcass and a limp pair of feet being ominously dragged around a dark corner. But coming from the Comedy Central funnyman, the ad seems more like a tongue-in-cheek jest than a legitimate character attack. “Mitt Romney has a secret,” says the narrator, John Lithgrow, who played a serial killer on the Showtime series “Dexter.” “As head of Bain Capital he bought companies, carved them up, and got rid of what he couldn’t use. If Mitt Romney really believes ‘corporations are people, my friend’ then Mitt Romney is a serial killer. He’s Mitt the Ripper.” MORE

PAUL KRUGMAN: Aha. Romney concedes that the estimates people have been making about his taxes are basically right:

At an event in Florence, SC, Mitt Romney told reporters that his effective tax rate is probably close to 15% because most of his income comes from investments, reports Bloomberg’s Julie Davis.

And an immediate question is, do you agree that unearned income should be taxed at a rate so much lower than earned income?  Besides, he’s still fudging: how much of that is true investment income, and how much is carried interest, which is actually earned income that for reasons unclear manages to get taxed like investment income (making nonsense of the claim that investment income should face low taxes because it has already been taxed once)?Oh, and don’t give me the argument that private equity is special because it’s a risky business, in which you put in a lot of effort for an uncertain return. So is any kind of small business venture; and so, as it happens, is textbook writing. Yet small businessmen and textbook authors pay normal tax rates. MORE