Take that, Hillary Clinton and John Edwards.

If I were the Obama folks I'd be a bit nervous to see John Kerry surfing into the picture with an endorsement, given how it worked out the last time a former Democratic nominee stepped in to back someone in the primary.

UPDATE: Precious line from Cillizza's report: "One former Kerry adviser, granted anonymity to speak about the endorsement before it became public, said that the Massachusetts senator has a "really, really great" organization in South Carolina that should help Obama in the state's Jan. 26 primary. (It's worth nothing, however, that Kerry lost the South Carolina primary in 2004 by 15 points.)"

UPDATE II: Jake Tapper reports Kerry didn't tell Edwards about the endorsement before it happened.