Robert Novak's election post-mortem:

The apparent Democratic takeover of both houses of Congress left Republicans stunned and divided, unable to comprehend that the nation's political realignment creating a GOP majority had crested and reversed. The confidence that relied entirely on a generously funded Election Day organization now looks like arrogance. The party's cocksure political mechanics simply could not believe the outcome as the results poured in.

Democrats capitalized on a mood that was not so much pro-Democrat as anti-Republican. Republican leaders are still in denial in the wake of their crushing defeat. They blame individual losing candidates for failing to prepare themselves for the election, but the real fault lies with the GOP's Washington establishment, which played its hand at Republican governance so disastrously that by Election Day Republicans could hardly get a cab ride anywhere in middle America.

Novak also brings up the interesting fact that all six GOP House members who left their seats to run for higher office — either for governor or the Senate — lost, while half their abandoned seats went to Democrats. His full post-mortem is here.