I would attribute the President's confidence to a clear victory. The man has sustained one of the vicious assaults, first by Moore and Soros types and finally by the mainstream media. Even on election day, the exit polls now leave everyone suspicious. Any one of the challenges he has faced would have taken a lesser man down and yet nobody but his supporters gave him credit for them, nobody provided the context with which to view the economy or the war.
President Bush deserves admiration for never whining, never responding in kind and never giving up his position in response to these assaults. Instead he believed in the American people. He must be inspired, his ideas and beliefs were clearly validated.