Nor is it a coincidence that these liberal policy victories have been accompanied by liberal gains in the culture wars. True, there’s no necessary connection between the Bush administration’s Iraq floundering and, say, the right’s setbacks in the gay-marriage debate. But cultural change is a complicated thing, built on narratives and symbols and intuitive leaps.

As The American Conservative’s Dan McCarthy noted in a shrewd essay, the Vietnam War helped entrench a narrative in which liberal social movements were associated with defeat in Indochina — and this association didn’t have to be perfectly fair to be politically and culturally potent.

In a similar way, even though Donald Rumsfeld and Dick Cheney weren’t culture warriors or evangelical Christians, in the popular imagination their legacy of incompetence has become a reason to reject social conservatism as well. Just as the post-Vietnam Democrats came to be regarded as incompetent, wimpy and dangerously radical all at once, since 2004 the Bush administration’s blunders — the missing W.M.D., the botched occupation — have been woven into a larger story about Youth and Science and Reason and Diversity triumphing over Old White Male Faith-Based Cluelessness.

Of all the Iraq war’s consequences for our politics, it’s this narrative that may be the war’s most lasting legacy, and the most difficult for conservatives to overcome.