I think the best thing Dean can do in the debate is open with a joke about his speech. Showing that he realizes it was over the top, and making it funny instead of embarassing will be a tremendous help. There's also the opportunity for a little self-effacing humor, which will soften the charges of egotism. So, here are some potential jokes...feel free to add yours (realistic or otherwise) to the comments.
"Before I answer the question, I'd like to take this opportunity to assure the people in the auditorium tonight that your eardrums are perfectly safe."
"When you're going into battle against George W. Bush, you better have a good war cry."
"Forget the debate...I want Holyfield! I want Holyfield!"
"Excuse me, but I specifically asked for a breakaway podium."