And certainly Keyes comes across as an intellectual heavyweight. But I believe he knows the right buttons to push to get Obama to say something he would rather not say. I don't think Obama can keep up with him.
Also, I don't see a downside for Keyes. If he loses the election, he will still walk away with more people knowing about the Declaration Foundation and very likely, more financial support for it and his other endeavors.
If you were Barack Obama, why on Earth would you agree to debate Keyes?
He may do it, but it serves him no purpose.
If I remember correctly, even before Ryan's marital "issues" surfaced, he was trailing Obama in the polls.