My guess is that a large number of those voting for BO in '08 aren't going to show up this time around...especially those "first timers" who were recruited merely to vote for him based on his race.
I certainly didn't think it meant the 800 billion worth of Tax Cuts that he signed and it doesn't. That $425 billion is actually the payroll tax cuts, eic tax cuts, student tax cuts and other stimulus tax stuff that he enacted/signed outside the $800 billion I am talking about. That is what the $425 stimulus tax cuts number meant.