While he is not ready to make a public announcement, John Maginnis reports Rep. Charlie Melancon (D-LA) has decided to run for the U.S. Senate. Sources say he "he has told national Democratic campaign officials" he will challenge Sen. David Vitter (R-LA) in 2010.
"While Melancon earlier this year seemed to have ruled out running, a renewed press by the Democratic Senatorial Campaign Committee, armed with a poll showing Vitter's vulnerability, got Melancon to reconsider."
This is a tremendous get for the DSCC, though of course holding Melancon's R+12 seat in LA-03 will probably be an extreme challenge.
UPDATE (James): Melancon is staying mum, but he says that he will be making a formal announcement "in the coming weeks".