Supporters of the war who don't have to engage in presidential debates with two-minute deadlines should feel free to acknowledge that if retrospective analysis is permitted, it is impossible to maintain that to have acted in March '03 was wise. But failure to justify the launching of the war does not discredit it. The French spring offensive in 1917 should never have been undertaken, but that didn't discredit the war. Field Marshal Montgomery's bridge-too-far air attack of September 1944 was disastrous, but didn't impair the Allied rationale.

President Bush is saddled with a war the evolution of which he can't retroactively reshape. His difficulty will lie in telling the public what should now be done. But this is a difficulty Kerry also has. Who has an answer to how to save the next American hostage from decapitation? The leverage Abu Musab al-Zarqawi has over U.S. thought and feeling is blindingly exploited by the simple sadism of the blindfolded hostage and the executioner's ax -- a viewer of the video reports that those screams will stay in memory forever. What is to be done about that?

Why is it taking so long to try Saddam Hussein? He was captured in December. Do they really need a thousand witnesses in order to establish his guilt? Why not schedule his beheading to coincide with the next beheading of an American hostage?

There is nothing Kerry can do in the campaign to persuade a majority of American voters that the way to compensate for mistakes of the past generated by unreliable intelligence is to abandon an enterprise to which we are morally committed. Abandoning Vietnam is a historic deed we have yet to reconcile with U.S. idealism. We handle that problem by the expedient of not thinking about it. But Iraq is a mind-filling challenge that can't be made to disappear.