Before the election, conservative pundits and politicians were pushing the meme that the United States is a "center-right" country, and they have stuck to that spin even after Obama's convincing victory. According to these conservatives, no political realignment has occurred, merely a one-time reaction to particularly bad Republican governance. Well, they have a point, but it's not quite the point they intend. Realignment is not occurring as fast as many Democrats would like to believe, but the problem is not a fundamental center-right orientation of the entire nation; the problem is political stasis among conservatives themselves.
Part of what it means to be a conservative is to resist change. Thus, the right and center-right wings of the country always will be larger than justified by the zeitgeist. "Realignment" analyses tend to favor the Republicans, and support the existence of the "center-right country" meme, simply because rightists are less flexible, and realign more slowly.
If you consider the quality of the 2008 national tickets, the enormity of the problems facing our country, and the demonstrated ineptitude of Republicans in authority, Obama should have won by a much greater margin. I am convinced that millions of people voted for McCain simply because their thinking is trapped in 2004, or 2000, or even earlier. They simply cannot adjust rapidly enough to cast their votes based on current realities.
Since Johnson's defeat of Goldwater, which was pre-Southern Strategy (the GOP's infamous, coded race-baiting), there has not been a true landslide win for the Democrats in a presidential election. Democrats can point to nothing on the scale of Nixon's drubbing of McGovern or Reagan's destruction of Mondale. But that's because the right-leaning bloc is more immobile than the left-leaning bloc.
Imagine Sarah Palin running against Obama in 2012. Now, imagine that the Democrats managed to find a presidential candidate as untrained, ignorant, and extremist as Sarah Palin, and put that candidate up against an experienced, intelligent, and conservative-but-reasonable Republican. I think our hypothetical dumb Democrat would lose by a much bigger margin than would Palin, because more left and center-left voters would prefer a candidate who was ideologically dissimilar, but at least basically competent, to a candidate who waved the correct flags but was plainly an utter fool. Thus, Democrats' greater flexibility and grasp of reality make realignments in our favor appear less dramatic and decisive.