GUEST is a little excited.

First of all, Bush is not "this far ahead in the polls." He is ahead in a single poll.   Second, as many have said, complete refusal to participate in debates will be perceived as weakness, and Bush will not allow that.

What he may do is set the terms of the debate so they are most favorable to him. But he will not completely withdraw from them. If he does, there is a good chance he will lose the election.