and stephen colbert goes to washington. he's going to be testing on something quite series. an expert witness today on capitol hill. he spent a day last month picking vegetables on a farm in upstate new york. part of a campaign to invite u.s. citizens to replace illegal immigrants who work on farms. well, the man who built president obama's historic 2008 presidential campaign is already thinking repeat. senior adviser david axelrod talked about his future saying he'll leave the white house sometime next year to start on the 2012 campaign. he didn't nail down a date on when he'd depart from the white house. and another white house departure, defense secretary robert gates saying he wants to leave next year. our senior political editor mark preston is following that for us live at the cnnpolitics.com