Historians and pundits will be picking through the 2008 election for years, but there seem to be four main factors that made an Obama win possible.
First, there is Obama himself. He put together an excellent team, developed an effective strategy, and was a master at presenting himself. He also excelled at damage control. Further, he has the traits that Americans are looking for in a leader: he is calm, rational, competent and confident. He also seems to be willing to take steps to bring Americans together, even to the point of possibly including Republicans in his cabinet.
Second, there was McCain and Palin. McCain has many virtues, but the ability to run an effective and strategic campaign is not among them. As the pundits pointed out, he had no overall strategy and seemed to lurch from tactic to tactic based on what day of the week it was and what tape or rumor about Obama happened to surface. Palin also seems to have been a slight drag on the ticket. Perhaps not enough to make a major difference, but enough to take votes away from McCain. Of course, it was impressive to see McCain keeping his campaign going. It was like watching a pilot somehow keeping a bullet ridden and burning plane in the air.
Third, there was the economy. As the pundits have said, if the economy was doing well and the #1 issue was security, McCain would have most likely won. However, McCain came across as weak on the economy and fumbled badly when the crisis arose. Obama handled the situation with more skill and succeeded in coming across as confident. Further, concern about the economy no doubt helped erode concerns about race. This is, of course, the classic foxhole effect. In times of such worry people care less about factors like race and more about whether someone can help them out. Obama did an excellent job convincing the American people that he can handle this crisis while McCain did not. Hence, the tanking economy gave Obama a critical boost by switching the race to McCain’s weak point and also dampening concerns about race.
Fourth, there was George Bush and the Republicans. Their actions lead to incredibly low approval ratings and to a damaged Republican brand. McCain not only had to run against Obama, he also had to run against the damage done by his own party. If McCain had been able to do more to separate himself from Bush, then he might have had a better chance. Amazingly, calling himself a maverick did not do this. Of course, McCain was in a difficult situation: he had to cozy up to the party to get the support and funds he needed, but had to distance himself from that party to avoid being dragged down. In the end, he was unable to make it work.