If the GOP had chosen McCain the moderate, things probably would have been OK. Problem is that McCain would need to take several giant steps to the right to be a moderate.
To be fair to federal__reserve's opinion I don't think it's possible to peg McCain as a rightist or a leftist. He's a McCainist. McLettucehead all the way.
McCain is the best example of a loose cannon I can think of. When the ship pitches starboard he slams into the starboard rail. When it pitches port side he slams into the port side rail. It is uncanny that he rarely seems to mow down a Democrat deckhand when he's careening to port side though.