Some of these contradict each other:
possibility 1) Our masters on Wall Street would first react with initial horror that McCain won, since they deliberately timed the crash to prevent him in particular from winning the Presidency. There would be a split, between those who insist on keeping the economy in depression and getting a Democrat in in 2012, and those who try to mitigate the damage done under a GOP government. Eventually, the narrative that might become dominant is that things are bad because of John Scapegoat McCain, not the GOP nor Wall Street.
possibility 2) The Democrats would very nearly dissolve, as being unable to win in 2008 implies a level of incompetence far too great for a major party.
possibility 3) If the Democrats don’t wither up and blow away, then the GOP would have to bribe the American people to stay in power. McCain could keep going back to Congress for more stimulus, and get 3-5 times as much stimulus by May 2012 as Obama did in his timeline.
possibility 4) McCain probably would clean up the CIA secret prison system.
possibility 5) Dems would very likely take the House in 2010, and hold it in 2012.