Mark Steyn says this is a typical 6-year election, with the opposition party underperforming compared to most six-year elections.
This year has looked like 1986 for several months. We lost a lot of close Senate races that year.
Krauthammer had an excellent article too about how this kind of thing usually happens at the 6 year mark. He said the bad news is the Dems will try to hang it on the war and Bush, when it is just a normal cycle of politics.
Well . . . that's one way to look at it.