Curious things have resulted from this imbalance between the ways the right and the left see the war. One is that conservatives could oppose invading Iraq without ceasing to be conservatives. [...]
On the left, however, to support the war meant, and continues to mean, that one must cease to count oneself on the left. After September 11, the blogosphere was full of people—Roger Simon is a good example—who insisted they were old-fashioned liberals who merely wanted a strong foreign policy. And no one on the left believed them, precisely because no one on the left could believe them. A use of the American military is necessarily a vicious thing, and opposition to the war is a marker of liberal credentials. Just ask Joe Lieberman, elected last night as Connecticut’s senator without a party.
The middle in American politics, the non-ideological voters, were always changeable. If the war went well, they would support it; if the war went poorly, they would lose patience. But [...t]he fact is that conservatives, too, were changeable on the war, and they varied as the result seemed to prove or disprove the foreign-policy theory under which we went to war.
Only the left wouldn’t change. [...E]ven if the war were working out easily, the people on the far left would oppose it in exactly the same numbers they now do. It isn’t that they reject American foreign policy, although that’s the effect. They reject the notion that this is a foreign-policy question. It’s a culture war, and they are looking to win here the battles in the culture wars they believe they have lost elsewhere.
I think he's got something, there.