Two points we have to keep in mind here:
- It wasn't the Democrats that won the elections, it was Obama. Make that very clear. It's a very clear distinction, that it was the Dems who rode on Obama's coattails and got the momentum they needed to get a few extra seats in Congress. That is made very clear by the fact that the Dems were not able to get the clear majority that they needed to become filibuster proof.
- It was Bush who had made the Republicans become the big losers of these elections. I can't think of any one other President in the history of the United States that had become such a liability on his own party, that any association to him, however near or far, almost meant the kiss of death for the candidates in all races. It's true that there were a lot of Republican incumbents that made it back into Congress, but those mostly came from Republican country where being a Democrat is tantamount to being a leper. Bush's legacy will be as a highly divisive leader, whose ideas of empire building were squashed by Obama's historic run to the White House.
One other thing, and I heard that on NBC during one of the interviews they had, that electing Obama does not make America post-racial, it means that a black man is elected President. I think that there are still a lot of racial problems and tensions in America that will take years and generations to heal and resolve.. if at all.