Conservatives and Capitalists have had a tough time embracing John McCain. There is a general feeling that he either doesn't really understand or doesn't support their general principals. He was able to sway many with his choice of Sarah Palin as his running mate, but what's going on right now will overshadow all of that.
McCain has made a great show of waving a pen around and stating that he will veto any pork barrel bills that come to his desk and "make the authors famous". Yet he's about to be a party to the biggest pork barrell spending bill in the history of the universe: The federal bail out of failing banks.
Democrats tend to stay loyal to their nominee regardless of how they vote or what kind of trouble they get into. Conservatives and Capitalist within the Republican party are conservative and capitalists first and will not support a Republican they view as ignoring their core beliefs. You can ask George Bush Sr. about that one. After his famous "Read My Lips, No New Taxes" pledge, he was convinced to sit down with Democrats and hammer out a new tax increase plan. His second term was gone as of that moment.
Conservatives and Capitalists will not vote for the Democrat. They will either vote third party or not vote if this bail out thing passes with McCain's support. Yes, we would rather see the country fall into depression than see it abandon free market principals just because things got tough. We're funny that way.
If McCain doesn't throw himself in the path of this bailout and do everything in his power to stop it, this election is over as far as he's concerned. If he doesn't understand that, he doesn't understand his base. Depression doesn't scare us. Obama getting elected doesn't scare us. Being in any way connected to the nationalization of private enterprise is something we simply will not do.