Obama's most comfortable in venues where people just admire his adorableness, like "The View," or a pizza restaurant where he gets a big hug. He's been campaigning like a little kid, called into the living room by his parents to show off for guests. All he has to do in such events is let the guests fawn on him.
Debates call for a little more than that, especially when the jive-talk and B.S. wear thin.