Disregarding the ideological bias of the writer, Jonathan Chait, he actually makes a few good points:

"Well, let's go to the exit polls. If Republicans lost because they abandoned conservatism, you'd see a big drop-off among conservative or Republican voters. Didn't happen. In 2004, 93 percent of self-identified Republicans voted for President Bush. This year, 91 percent voted for their GOP House candidate. The percentage of voters who identified themselves as conservatives barely budged, falling by just two points, from 34 percent to 32 percent, according to exit polls.

All the GOP losses occurred in the center. In 2004, Bush lost among independents by just a single point. In 2006, independents voted Democratic by a massive 19-point margin.

When conservatives try to get more specific about why voters turned against them, their explanations make even less sense. Jeff Flake of Arizona, a leader among conservatives in the House, suggested that his party apologize to voters like this: "We've overspent, badly, and it was offensive to you as well as our conservative principles."
But exactly how have Republicans overspent?

The largest spending increases under Bush, by far, have come in defense and homeland security, which conservatives support. The next biggest item is the Medicare bill. Horribly designed though it was, you can't say it was unpopular. Poll results indicate that about 90 percent of the public support adding prescription drug coverage to Medicare."

Although, he does fail to acknowledge the possibility that Republicans might have lost among independents because of spending increases, overall this seems to lead to the conclusion that Congressional corruption, voters' desire for change, Congressional competence, and Iraq amongst other issues played a more major role than spending.