This debate will make or break McCain, count on it.
This is his supposed strength, the town hall format. I think he is full of shit and if anyone asks him a bad question, I expect him to revert back to Angry John and say something stupid. Seeing as how he has more than lost his temper the past few days, I will not put it past him to say something extremely dumb.
If the debate is in Obamaland, like tiesto said, that will give a populist impression that the people are for Obama. That is the point of the town hall debates. So I expect Obama to walk away with this one.
If in the rare chance McCain wins, I think he will become viable again. The GOP is desperately hoping for a miracle and if McCain gets it in the form of a victory, I expect the momentum for Obama to stop dead and become more competitive.
If McCain loses, which is the likely chance, I don't expect much support for him anymore. Losing 2 out of 3 debates, 3 if you count the VP, the momentum will be so much against McCain that I expect the focus of the RNC will begin to move more towards making sure Senators like Liddy Dole and Norm Coleman remain in office or in short, making sure they can maintain their GOP base as best as they can.