Even relatively conservative incumbents who have done well for their constituency have been tossed out in favor of unknown Democrats claiming to be at least moderate, and conservative on some issues. They got caught up in the rush to "throw the bums out".
The Republicans brought this upon themselves, and they have no one else to blame. I was terribly disappointed in the choice they made to replace Frist, who I was not happy with. Corker was certainly far less of a good candidate than either of the two he beat in the primary, but the party backed him. So he got elected. Then he had Ford for competition and barely beat that scumbag. It was the same in many places.
In the two close Senate races that it appears will give the Democrats control over the Senate as well as the House, the difference will likely turn out to be those disgusted Republican supporters who stayed home.
If the Democrats didn't really suck, they'd have easily beat the average and a lot more Republicans would have gone home.