He is arguing for a middle way between Obama's and McCain's campaign positions:

Democrats and other war critics should not be arguing for an unconditional and rushed departure, as the congressional leadership and Obama are generally doing. Nor should supporters of the war be arguing for a largely open-ended commitment regardless of Iraqi performance, as the Bush administration and to some extent Sen. John McCain seem to favor. McCain, the GOP nominee, has been vindicated in his support of the surge, and his resolute commitment to success in Iraq is admirable. Yet it is better that Iraqis also hear a U.S. message of tough love, not only what has essentially become an unconditional promise of assistance. Democrats can provide such a melded approach. If Iraqis do their part, we help; if not, we leave.

But here is the critical caveat:

Those who say Iraq will be better off once we leave underestimate the typical duration of most nation-building efforts (a decade or more) as well as the fragility of Iraq's new institutions and the freshness of sectarian wounds that have only begun to heal.

My emphasis. So how do we provide a real message of tough love if the Iraqis know and we know and they know we know that a decade more is about the minimum required to construct something like a non-failed state in Iraq - and even then, it is a highly dubious project?

That's why this is so hard: because the middle ground is far more expensive and open-ended than anyone has so far explained candidly to the American people. It seems to me that those who favor withdrawal need to be honest about the conflict that would follow and argue how we can live with it, or play it to our advantage. And those who insist we should stay until Iraq exists as a unitary non-despotic country have to be honest about the decades-long effort this will require. Maybe then we can conduct this debate more intelligently. And that's one more reason to hope the primary season won't stretch into the summer. The bigger debate between McCain and Obama is one we all need.