From LiberalValues[HERE] Adding Hillary to the ticket would not bring Obama a single vote (except possibly for Bill’s). Her supporters are divided into two distinct categories. The original Clintonistas were strong Democrats, party faithful, pro-choice, middle-aged and up, largely female and all white. But Hillary’s recent backers have been downscale whites of both genders who were turned off by Obama’s pastor, wife and other associates and were afraid he might be a Muslim in disguise. Unhappy about voting for a woman, they never really liked Hillary but turned to her when the alternative was Obama. If Hillary had won the Democratic nomination, these latent backers of Hillary in the primaries might still have voted for McCain in the general. Their support of Hillary is purely linked to her opposition to Obama. Were she to join the ticket, they would vote for McCain anyway. After all, Obama will still be black and the Rev. Wright will still be nuts.

How he did it
According to Taegan Goddard's Political Wire "the 2008 presidential campaign has produced its share of surprises, but one of the most important is that a newcomer from Chicago put together by far the best political operation of either party. Obama's campaign has been that rare, frictionless machine that runs with the energy of an insurgency and the efficiency of a corporation. His team has lacked what his rivals' have specialized in: there have been no staff shake-ups, no financial crises, no change in game plan and no visible strife. Even its campaign slogan -- 'Change we can believe in' -- has remained the same."