If McCain gains momentum from his performance tonight, he has to do it by hitting the trail tomorrow hammering the points he hammered tonight. He has to fire his campaign, turn Palin loose, and rally his supporters to his cause. He has to have his face in the media every day making the points that he needs to make. He has to put Obama on the defensive and keep him there until 4 November.
Again, if McCain does this, he wins, if he does not, he loses.