There's little doubt that "What to do about Iraq?" is the central issue in American politics today. It isn't the only issue -- witness illegal immigration -- but it towers above all the others. It is costing $250 million a day, and several American lives a week, and polls make it clear that the American people are thoroughly (and, I might add, understandably) upset about the way it's going.

How we got here isn't in doubt. President Bush (like President Clinton, and all of the leading spokesmen of both parties, and for that matter all of the major nations of the Western World, and the United Nations) was convinced in 2003, on the basis of the best intelligence available, that Saddam Hussein had chemical and biological weapons of mass destruction, and was moving to construct nuclear weapons as well. In those circumstances, and given the spectacular failure of diplomatic efforts to discipline Saddam, Bush would have been irresponsible if he hadn't ordered a military attack to overthrow and replace Saddam's regime.

When it turned out, however, that no such weapons could be found, Bush pointed out that Saddam was a murderous tyrant who thoroughly deserved ouster anyway. And far more important, if a democratic successor regime could be brought to birth in Iraq, the beneficent effect on the whole Middle East would be enormous. The example of a free Arab society would resonate throughout the region, force democratic reforms in all the neighboring states, and stabilize this important corner of the world for decades to come.

Since then, the United States has been trying grimly to bring about this hoped-for result. But the fanatical Islamist insurgency, traceable to Osama bin Laden and led in Iraq, until recently, by Abu Musab al-Zarqawi, has made the going far rougher than Bush and Secretary of Defense Donald Rumsfeld can ever possibly have anticipated. Suicide bombers and gratuitous beheadings have made the process of winning maddeningly slow. But have they made it impossible? That is the question that understandably preoccupies American politicians.

For the Republicans, the answer simply has to be "No" -- Bush has committed the nation to war, and the only acceptable outcome is victory.

For the Democrats, however, there are other possibilities. Without going so far as to wish defeat upon America's forces, they may conclude that victory is not, in fact, possible -- not, at any rate, at any price the nation is prepared to pay. In that case, prudence would dictate withdrawal, and if that resulted in almost unimaginable disaster for American foreign policy and America's image in the world -- well, the responsibility would be assigned to Bush and the Republicans.

So the Democrats today are searching desperately for a policy, and the surprising news is that they are split six ways from Sunday. A few, like the indomitable Sen. Joe Lieberman, D-Conn., insist that the war is winnable, and support Bush's determination to press on. Most of the rest suspect that it isn't, but are deeply divided over what to recommend. Sen. John Kerry, D-Mass., wants to start pulling out American forces by the end of this year. Others demand that we "redeploy" our troops beginning on some later specific date (e.g. June 30, 2007). Sen. Hillary Clinton, D-N.Y. -- if I understand her -- also favors "redeployment," but without a specific timetable.

And all of this leaves unclear exactly what "redeployment" means. Would our troops be redeployed to their bases in the United States, or simply across the Iraqi border into Kuwait, to await orders for further military action? The Democrats don't say, and take refuge in the comforting ambiguity of the term.

But it's hard to imagine a bumper sticker summarizing that mishmash of contradictory ideas. "Bug out -- but slowly"? "Bring the boys halfway home by Christmas"? The Democrats must have the courage of their convictions, but first they have to decide what those convictions are.