Thanks to George Soros and others, Obama will have upwards of half a billion dollars to spend on attack ads. He outspent Hillary but still lost most of the late primaries, but he’ll have an even larger advantage facing McCain...plus the media will be entirely on his side, whereas it was divided when the race was between Obama and Hillary.
And all that money isn't going to buy them the Presidency. It hasn't yet. I can't see it happening this time either.