It was a sucker pitch, and John Kerry fell for it like a rookie. I’m talking about President Bush’s latest cheap gambit–turning his own unjustifiable and costly invasion of Iraq into his opponent’s problem. Bush mocked Kerry’s Iraq position for its “nuance”–a word that manages to sound both French and less than fully masculine.

At Bush’s prompting, reporters asked Kerry if he, knowing what we all know now about Iraq’s lack of weapons of mass destruction, would still have voted, as he did in October 2002, to authorize the President to use force against Iraq. Instead of smacking that hanging curveball out of the park by denouncing the Bush Administration for deceiving Congress and the nation into a war, Kerry inexplicably said yes.

Of course Kerry went on to make an important critique of Bush’s conduct of the war, but he got slammed by the Bush team as well as the media for losing in the “gotcha” derby.

The irony is almost too much to bear. After all, for two years Bush has flip-flopped relentlessly on just exactly why it was a good idea to occupy a troubled Muslim country that posed no military threat to the United States. Now Bush is getting political mileage out of exploiting Kerry’s stubborn refusal to admit he was had by All the President’s Con Men.

The fact is, Kerry has been consistently saying the same thing for two years: Based on the Administration’s claim that Saddam Hussein was linked to Al Qaeda and possessed WMD, the President needed the stick of the use-of-force authorization to compel Iraq to comply with UN resolutions.

That explains the “yes” vote, but unfortunately, then and now, it is the wrong answer to the wrong question. Kerry should have known by the fall of 2002 that Bush was hellbent on invading Iraq and that to do so would severely undermine the war on terror. Everything emanating from the White House at that point made it clear that the President was highly unlikely to be satisfied by simply securing a new UN inspections regime.

At a minimum, Congress had a responsibility to hold hearings to examine intelligence on Iraq, which even then was causing enormous tension between intelligence analysts and spinners in the White House and Pentagon. After all, the Constitution is as clear as the framers could be on the primacy of Congress in declaring war. Kerry and the rest of the Congress should have considered the facts, even if the White House refused to do so.

This was doubly true after the UN inspectors were allowed back into the country and given unprecedented access. And here is where Bush and Kerry’s positions on Iraq diverge.

“I thought we ought to reach out to other countries, we ought to build an international coalition, we ought to exhaust the remedies available to us,” Kerry pointed out last week.

Bush uses the word “nuance,” but the difference is huge because the most bizarre aspect of Bush’s march to war and occupation was his argument that we couldn’t wait a few weeks for UN inspectors to finish their search for those nonexistent doomsday weapons. Didn’t we owe it to the teenagers we were about to send into battle in a foreign land to “exhaust the remedies available to us”?

Some justify Kerry’s refusal to recant on that “yes” vote–a vote he must now know was unwise–on the grounds that if he speaks the truth he will lose swing voters who value a strong America. But this is malarkey: Half the country now thinks invading Iraq was a bad idea, and nobody can be comfortable with the way it’s turned out. The American people want to know how we got into this mess, how we can get out and how we will avoid making such stupid mistakes in the future.

To win the debates and the election, Kerry needs to establish himself as the clear alternative to a President who has lied us into a quagmire. His forthright speech at the Democratic convention shows he is capable of this: “Before you go to battle, you have to be able to look a parent in the eye and truthfully say: ‘We tried everything possible to avoid sending your son or daughter into harm’s way. But we had no choice. We had to protect the American people, fundamental American values from a threat that was real and imminent.’ ”

Kerry’s got it right then. But it won’t matter if he continues to whiff on Bush’s curveballs.