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.
There are ways to force debates.
And even if you don't succeed, there is alot of political mileage that can be made by a candidate's refusal to do so.
But the people in this state have a bad taste for Ryan's - starting with the last governor of that name. Moral turpitude of an elected Republican official will keep social conservatives home for years. And when the GOP keeps running people of the same name and people with other moral "issues" it brings all the past forward and it snowballs.
Keyes is clean, is not a "Ryan" and is truly a social conservative. The people who elected Fitzgerald can still be inspired to vote - but it'll take a lot of work.