I see McCain's move to postpone the debate as an act of desperation, but I'm sure he intends it to be seen as if he was doing something "presidential".
McCain isn't president now, is really having him gone for a few hours from Washington really going to affect the economy in anyway? Can he walk and chew gum at the same time?
If he doesn't have the time then he should send Palin to stand in for him in the debates. It would be a great way to eliminate any lingering questions about whether she's qualified for the job. The first debate was on foreign policy, what a better time to talk about the view from her house.