I think Suzanne Nossel puts things into the proper perspective as she wrings her hands and observes,
Like Nossel, I think we've passed the point of no return. According to Sy Hersh, the Israelis concluded already two years ago (once it became clear that the U.S. was facing an insurgency) that the U.S. had effectively already lost --and have responded by working to secure a friendly Kurdistan out of the Iraqi rubble.
1) public support for the war's dwindling; 2) without strong public backing war becomes untenable; 3) we can't cut and run for fear terrorists will be emboldened and that Iraq itself will descend into chaos dragging down the region; 4) our very presence in-country seems to be fueling the insurgency; 5) we cannot up the number of boots on the ground without instituting a draft or similar; 6) no other countries are willing to ante up troops to help us and, under the circumstances, its hard to blame them; 7) training of Iraqi troops and police is much slower/harder than expected; 8) even if one gives up on the hope of a liberal democracy in Iraq in the short or medium term, the goal of a base level of stability to allow U.S. exit within the next 2 years or so looks out of reach; 9) the political process has bogged down to a point where its unclear whether a unified state will emerge.
As progressives, we've argued at every turn against the decisions and actions that led us to this quagmire. The longer our advice is ignored, the tougher it becomes for us to say what to do next (one of Kerry's problems during election season).
If this is true, then the strategy now should be to leave as soon as possible. No need to set an official timetable for withdrawal; simply delcare victory and start pulling the boys out steadily, much as we did in Vietnam from 1971 forward. Politically, to encourage this choice, the Democrats should argue that, "The war may or may not have been a good idea in the first place. The war may or may not have been winnable when we launched it in April 2003. But now, given the way the war has been waged (with not enough troops on the ground in the first place, with the botched security and infrastructure situation in the immediate aftermath of the war, and with the scandals of Abu Ghraib and Guantanamo), now the war is lost. From here on forward, every further American who dies in Iraq is dying not to make victory possible for his country, but only in the vain attempt to salvage George Bush's historical reputation." Of course this position will be attacked as defeatist, and progressives would just have to have the courage to deal with that.
However, there is another possibility, one that Juan Cole put forward last month, namely that we're "just screwed": we may not have passed the "point of no return" and definitively lost, but we certainly face a 10+ year insurgency, one that we should expect will cost 10,000 Americans lives... after which we still may not "win" (in the sense of establishing one or more stable, prosperous, pro-American states in Mesopotamia).
If you believe this is the case, then clearly BushCo should have the courage to say this to the American people, and hope the American people will keep re-electing them. However, it seems pretty clear the Bushies believe that to come clean in this way -- implicitly admitting that they radically miscalculated to begin with -- would result in a royal political shaft at home. And failing to come clean about the long-term costs of the war makes it much harder to sustain the pressure on the insurgents that would make victory even a hope.
Which path you take -- (1) cut and run; or (2) stay the nasty, brutish, and long course -- really depends on two variables: how central you think the Iraq war is to American security, and what you think the chances of "victory" are if we choose (2).
Personally, I think the chances of "victory" in Iraq are so slight, the costs of "victory" so high, and the geopolitical importance of "victory" so questionable, that choosing to cut and run seems like the only reasonable option. It will be a moral stain on our nation, to be sure. But it doesn't seem to me that allowing ten thousand more Americans to die will make the eventual disaster any less of a moral stain.
But what about emboldening the terrorists?! people will cry. What I like to remind the cassandras who worry about the disastrous geopolitical consequences of leaving (not all on the right: see Nossel's point 3, above) is that things may not, and in all probability will not, work out nearly as badly as you think. Remember how the hawks warned that if we lost in Vietnam then all of Southeat Asia would fall, and that eventually we'd be battling the reds on the shores of Malibu? Didn't happen.
In fact, in the larger scheme of things, the GWOT may not be all that important. The larger geopolitical and historical issues are the massive economic imbalance in the global economy, and relatedly, what the economic rise of China (and India) means for geopolitics. It may well be that, whatever the outcome in Iraq, the way the war will be remembered is mainly as a massive, costly distraction for America that accelerated the pace at which China reasserted its traditional position as the center of world civilization.
Finally, the question of what to do in Iraq is in some sense moot. It's clear that for the next three years Bush, if for no other reason that domestic politics (and he never needs any other reason for anything he does), will refuse to choose either of these "reality-based" possibilities. Between now and 2009, therefore, we should expect that at least a thousand more Americans will die, that ten thousand more will be maimed, and that perhaps a hundred thousand Iraqis will suffer similar fates. By failing to choose either "reality-based" option, moreover, Bush makes the option of effectively winning against the insurgents ever more costly, so that by the time we get someone more responsible in the Presidency (let's hope in 2009), they in all likelihood will have no choice left but to cut and run.
So that, in the long light of history, seems likely to be George Bush's (and early 21st century America's) geopolitical legacy: a massive mis-reaction to the tragedy of 9-11 that accelerated the return of Chinese global dominance.