"The [Democratic] party's leadership and political thinkers," writes Yglesias, "simply can't conceive of national security issues as anything other than a source of potential political problems to be coped with, never as a set of potential political opportunities."
Welcome to the learned helplessness of the Democratic Party. They've been spanked on national security for so long that they literally cannot conceive of pulling out a win merely because their position commands overwhelming public support. At best, the reprisal will be delayed a few years, until the Right convinces a fickle populace that the Reid-led withdrawal lost the war for us.
And it's almost hard to blame them. Hawkishness holds court as the default correct position in national security politics. Save, possibly, Curtis LeMay, I can't think of a single figure reviled or even mocked for excessive warmongering. Meanwhile, the ground is littered with dovish Democrats, from McGovern to McCarthy to Dean. Scoop Jackson, for no particular reason, is far more revered than William Fulbright. It's a sick and twisted tendency, and it manifests constantly, as in the Fineman column discussed earlier today, where McCain's poor accuracy in evaluating foreign policy outcomes is ignored and his enduring hawkishness and "moral seriousness" grant him the status of wise old national security man.
To keep this from being too unrelentingly pessimistic: Iraq is an opportunity. There just needs to be follow-up. If Democrats successfully close out the war and then let the right wing recapture the national security discourse, they'll end up tarred, feathered, and publicly trashed once again. But if they end the war, continue investing in the progressive national security infrastructure, and systematically work to turn the public's disgust with Iraq into a larger critique of warmongering imperialistic overreach, you could see the beginning of a more durable advantage for the Left. There are a lot of "buts," "ifs," and "coulds" in that sentence, though, and my sense of the Democratic foreign policy infrastructure does not leave me with a whole lot of confidence.
Update: Also, what Kevin said.