Gerald Seib pinpoints the cause of President Obama's summer polling collapse:

To grasp the importance of the summer's debt negotiations—which produced a plan to cut the federal deficit by at least $2.1 trillion over the next decade just in time to avoid a default by the federal government—look at both how the deal affected Americans' confidence, and how it is judged by them in a new Wall Street Journal/NBC News poll.
As Mr. McInturff notes, consumer confidence in the wake of the debt deal sunk to its fourth-lowest reading since 1952, as measured by University of Michigan consumer confidence index. Moreover, this drop in confidence wasn't some slow decline, but an immediate plunge clearly related to the debt deal and financial markets' reaction to it.
Between June and August—the stretch run of the debt talks—the Michigan confidence index plunged to 55.7 from 71.5.
That 15.8-point drop matches almost precisely the drop in consumer confidence seen after the Iranian hostage crisis, Iraq's invasion of Kuwait and the collapse of Lehman Brothers, and is close to the one seen after Hurricane Katrina.
"Make no mistake," Mr. McInturff says, "this collapse of economic confidence is not an independent event driven only by economic reality. This sharp a drop in consumer confidence is a direct consequence of the lack of confidence in our political system and its leaders."

The debt ceiling hostage crisis was a political catastrophe for both Obama and Congressional Republicans. He came away looking weak. They came away looking crazy. The episode, though, had more than political ramifications. It had economic ramifications. Confidence in the economy -- the number one conservative explanation for economic weakness -- took a real and justified plunge.

The Republicans pursued a strategy that torpedoed the economic recovery, and, indeed, may well bring about a double-dip recession. Voters may punish House republicans at the polls in 2012, but they're at least as likely to punish Obama. That Republicans may gain the White House on the shoulders of a Republican-induced recession offers lessons about the incentive structure of our divided system of government that are frightening to contemplate.