Packer has written an important piece in the New Yorker on the planning which has not happened yet, on how to get out of Iraq. I recommend it as required reading. I must admit to some mystification at this paragraph (emphasis added):

Bush will likely use Petraeus’s testimony, and his military prestige, to claim authority for sustaining the largest possible American presence in Iraq through the end of his Presidency. But how large could that presence realistically be? Currently, there are a hundred and sixty thousand troops in Iraq. The natural life of the surge will end in 2008, when the brigades sent earlier this year will finish their fifteen-month tours and return home. After that, it will become virtually impossible to maintain current troop levels—at least, for an Administration that has shown no willingness to disturb the lives of large numbers of Americans in order to wage the war. Young officers are leaving the Army at alarming rates, and, if the deployments of troops who have already served two or three tours are extended from fifteen to eighteen months, the Pentagon fears that the ensuing attrition might wreck the Army for a generation. Activating the National Guard or the reserves for longer periods could cause the bottom to fall out of public support for the war. Beyond these measures, there are simply no more troops available.
A Reporter at Large: Planning for Defeat: Reporting & Essays: The New Yorker

Excuse me?! “Could cause the bottom to fall out”! With support down to the high 20%s, how much more could it fall?