It's entirely possibly to both have the debate, and solve the economy problem. Neither Obama nor McCain are financial experts - they'll just be nodding their heads in meetings while Dodd and others who know what they're tlaking about, are doing the decision making.
This lets McCain bail out of a debate. After all the talk of "why won't obama have a town hall meeting?"
Maybe when he's president, McCain will learn to balance 2 things at once?