A year and a half later, though, violence is down dramatically and there's a cautious hope that both the U.S. and Iraq could achieve an outcome once seemed out of reach.

The surge didn't do all of that; a cease-fire by Shiite militias and the switch by Sunni insurgents from attacking Americans to fighting al-Qaeda helped enormously. But the extra U.S. troops, brilliantly deployed by Gen. David Petraeus, have made a huge difference in calming the chaos. In doing so, it also contributed to the other developments.

Why then can't Obama bring himself to acknowledge the surge worked better than he and other skeptics, including this page, thought it would? What does that stubbornness say about the kind of president he'd be?

In recent comments, the Democratic presidential candidate has grudgingly conceded that the troops helped lessen the violence, but he has insisted that the surge was a dubious policy because it allowed the situation in Afghanistan to deteriorate and failed to produce political breakthroughs in Iraq. Even knowing the outcome, he told CBS News Tuesday, he still wouldn't have supported the idea.

That's hard to fathom. Even if you believe that the invasion of Iraq was a grievous error  —  and it was  —  the U.S. should still make every effort to leave behind a stable situation. Obama seems stuck in the first part of that thought process, repeatedly proclaiming that he was right to oppose the war and disparaging worthwhile efforts to fix the mess it created. Hence, his dismissal of the surge as "a tactical victory imposed upon a huge strategic blunder."

The great irony, of course, is that the success of the surge has made Obama's plan to withdraw combat troops in 16 months far more plausible than when he proposed it. Another irony is that while Obama downplays the effectiveness of the surge in Iraq, he is urging a similar tactic now in Afghanistan.

As for the surge not producing sufficient political reconciliation in Iraq, it's true that efforts to integrate Sunnis into a Shiite-dominated political culture are only inching forward. But reconciliation takes many forms, and Shiite Prime Minister Nouri al-Maliki's military attacks against rogue Shiite militias in Basra and Baghdad's Sadr City were a hugely important signal to Sunnis.

Perhaps it's too much to ask that Obama risk being taunted by headlines such as "Obama says Bush was right."

But for the nation to move forward on its single most vexing debate, it would help if the next president could admit the obvious  —  whether that's Republican John McCain conceding that it was a terrible blunder to invade Iraq in the first place, or Obama acknowledging that the surge has worked better than he expected.

Americans don't expect their president to be right all the time. They do expect him to change course when he's proved wrong.