McCain wasn’t the best, he was the status quo. It is almost like the Physics theory of conservation of energy, objects will always move to the lowest energy state.. well politics will always move to the status quo state.
IMHO, the people behind Obama picked McCain as the most beatable candidate. Remember when he was out and then back in the primaries? It happened here in Illinois when Glenn Poshard ran against Blagoyavich. How well did that turn out?