Obama probably wins regardless, but the "shutting down the campaign" thing probably did more damage than any one factor. I was also struck by contemporaneous accounts of the meeting that Bush had with Obama/McCain at The White House and how even the Bush people seemed to feel McCain was out of his depth on the subject of the collapse.
McCain was a gifted politician and a true statesman, but he was a foreign policy guy arguing the status quo (ie. largely unpopular at the time) running in an election dominated at the end by financial issues and the economy. Even setting aside the poor fundamentals for any GOP candidate, the election cycle didn't play to his own personal strengths at all.
As for Palin, my best guess is that she was a wash. She may have brought out a few more conservatives, but I seem to recall at the time that, by the end of the campaign, she wasn't all that popular with the general public as a whole. But I'd have to look that up, it's been a while