In passing a resolution demanding that America's combat forces in Iraq be withdrawn by September 2008, the House Democrats have placed a heavy bet on the outcome of developments there, and a lot of political consequences will depend on the success of that bet.

Never mind that the resolution passed by only the narrowest of margins (218-to-212), with a significant minority of Democrats voting against it. Never mind that is it virtually certain to be defeated in the Senate, where the rules will enable the Republicans to filibuster it to death, if necessary. Never mind that, even if it somehow passed both houses, it would promptly be vetoed by President Bush, and that there is no hope of two-thirds of either house voting to override his veto. Speaker Pelosi and her colleagues knew all these things, and passed the resolution anyway, so they were voting to make a point.

Their point is that they believe the war in Iraq is irretrievably lost, and that continuing the battle into the indefinite future will merely waste still more blood and treasure. Moreover, they have seen the polls indicating that a majority of Americans agree that the effort in Iraq has failed, and the Democrats are therefore convinced that the voters will forgive them, in any case, for demanding a pullout. There is no political party more resolutely virtuous than one that believes a majority of the voters is firmly on its side.

The Republicans warn that the Democratic resolution is simply a prescription for losing the war. Moreover, they do not agree that it is necessarily and inevitably lost. President Bush has changed Defense secretaries, endorsed a new proposal for a surge in the number of combat troops in Iraq, and sent there to command the effort Gen. David Petraeus, who firmly believes that such a surge will work. What's more, the Republicans are aware that Americans reserve the right to change their minds. According to the polls, a majority favored the attack on Saddam Hussein's Iraq. Those same polls now report that a majority have lost heart. But if the surge succeeds, you can be sure that a majority will favor firm steps to wrap up the victory, and will be glad to scrap the Pelosi deadline.

The Democrats are aware of this possibility, but are simply betting that it won't happen. And even if it does, they calculate that the resulting situation won't be so encouraging that determined pessimists will be fatally embarrassed. There will still be problems with the Iraqi government, and enough fatalities among American troops to keep the media busy. The Republicans may rightly claim "victory," but the Democrats will continue to mourn the cost.

Meanwhile, of course, the very passage of this resolution by the House, regardless of its further prospects, will encourage America's enemies in the Middle East to believe that they are winning, and redouble their efforts. And indeed, in a sense they are winning, since the members of one of America's two major parties have called, in the House of Representatives, for our troops to abandon the battlefield. Wouldn't you like to see Osama bin Laden's expression when he sees that on Al Jazeera?

Still, a realist would have to concede that the chances are that the Democrats will win their bet, or at least escape major damage if they lose it. American forces have spent four years trying to devise a way of suppressing the terrorist insurgents that have killed so many scores of thousands of their fellow Iraqis, thus far with notable lack of success. It seems unlikely that a military "surge," however well conducted, can reverse that record. And even if it does, the Democrats are entitled to hope that the American people will choose to turn over the management of America's future in the Middle East to a party not compromised by the failures of the Bush administration.

A vigorous Republican presidential candidate in 2008 might convince the voters otherwise. But who is he? Am I the only one who thinks the newest face in the Republican race, former Sen. Fred Thompson of Tennessee, might just fill the bill?