It’s really two questions:
What would John McCain have done differently, that lead to different results? QE1 but not QE2? A bigger stimulus? A smaller? Raised taxes? Lowered them? Much of the economic momentum was already in place. Even if McCain had different ideas at the beginning, would economic realities have forced him into the same strategies? Note how far Obama has deviated from his campaign promises, out of necessity.
And then the hardest issue: if McCain’s wouldn’t have been able/tried to do much differently– if the results would have been the same– then is the fact that there aren’t London riots here in the US due to the perception that this President is for the people, while McCain would have been perceived as “for the corporations?” If John McCain was President, would Detroit and Philadelphia be on fire?
Has “the system” bought itself the necessary four years it needs to deleverage safely– to fire people, to reduce labor costs? Carter into Reagan? Have we avoided real social unrest because we have a black President?