He said that to a woman he knew was "close to" Rubio after she said "maybe" to his question "Is your boy going to go for [vice president]?"
That's one story in Politico's new e-book "Obama's Last Stand."
There's other interesting stuff at the first link, including Obama's disrespect for Romney — who stands for “nothing” — and his fear that Romney will get to "take credit when the economy turns around." There's also a lot of fairly generic material about the troubles in the Obama campaign. Axelrod got mad at Stephanie Cutter. An internal polls showed people don't like hearing from Debbie Wasserman Schultz. That sort of thing.