By most measures, the Iraq war has been a huge foreign policy blunder, exacting a huge cost in terms of American wealth and lives, and providing very little return on that investment. In fact, if the goal was cheaper oil, the war has been a spectacular failure. Prior to the escalations in tensions leading up to the March 2003 invasion, oil was ~$30/bbl. Now it's ~$120/bbl. To be sure, there are lots of reasons, in addition to reduced oil production from Iraq, and increased Middle East instability engendered by the war. Certainly one of those other reasons is the dollar's devaluation, and one could easily argue that the Iraq war played a large role in that devaluation - the government has been unwilling to fund the war and the rebuilding effort with cuts elsewhere. Turns out the federal government isn't much different from the overleveraged US consumer - spending money it doesn't have.
OK, so here we are in 2008. What do we do now? Some Americans want us to stay the course and win in Iraq. What exactly constitutes winning anyway? A stable government that can defend itself from internal attacks? What about internal attacks supported by external sponsors (e.g., Iran)? We haven't seen anything from the Iraqi military that shows their ability to fight successfully without American support on the front lines. There are reports that the training is inadequate, that their weaponry is inferior, etc.
I'll offer that there is a bigger problem. The Iraqis know that the Americans will leave. And they know that once the Americans leave, the government may be overthrown. As long as there is a risk that plays out, why would an Iraqi soldier want to piss off the guys who are going to decide his fate? In fact, the Iraqis know this story all too well. During the Gulf War, America encouraged the Shiites and Kurds to rebel. They did, and the rebellions were brutally crushed by Hussein, and we didn't protect them. Oh sure, we had a no-fly zone, but that was limited to fixed wing aircraft. So Hussein just used helicopter gunships. The lesson they learned is that they cannot rely on America to protect them.
Need another example of the risks facing the Iraqi soldier? Look at Vietnam. After the NVA and VC captured Saigon, thousands of South Vietnamese suspected of collaborating with the Americans were executed. Some of the various factions fighting the Iraqi government aren't even waiting for the US military to leave. Through their sources in the military, they are obtaining the names of soldiers and threatening their families.
So what's an Iraqi soldier to do? Fight for this new government, knowing that its main backer is leaving eventually, and that the very guys he is fighting could be taking over. Plus, run the risk that his family is executed at any time. Or, does he fight half-heartedly, just trying to collect a paycheck, and deserting at the first sign of danger to himself or his family.
Don't think we're leaving if McCain is elected President? Think again. We are fighting a war we cannot afford to fight - I'm speaking in financial terms - unless we are willing to face very deep cuts in the government's spending domestically and increased taxes. We've been having our cake and eating it too since the war began, but we've paid the price in terms of the dollar's value. I think once Americans are faced with the harsh reality that spending in Iraq means less spending domestically (the alternative is a banana republic currency), we will choose spending domestically.
OK, so maybe you agree that we cannot fight indefinitely, but perhaps we can crush the insurgent groups in the next year or two? Not gonna happen. Here's the basic problem We are fighting on another people's homeland without a strong moral justification. Just as Americans would rebel and never fully accept a government that was propped up by an invading power, the insurgents (both Iraqi and Arabs, who view occupation of any Arab lands by infidels as justifying jihad) are willing to die for their cause. We are not willing to die for our cause; that begs the question of what exactly our cause is? Hmmm, does that remind anyone of a certain war in SE Asia? Speaking of which, we learned, or should have learned, that lesson in Vietnam. From a military perspective, the US and SVA were absolutely annihilating the NVA and VC, but that didn't stop North Vietnam. Even after the initial peace in 1973, the North continued to attack, risking a resumption of US bombing, and after this never materialized, they were able to overrun the South. And if we didn't figure it out then, we had an opportunity to learn from the Soviet Union's occupation of Afghanistan. Even without a contentious media back home to deal with, the Soviets, who were presumably less constrained in their military tactics, couldn't defeat the Afghans and Arab insurgents. The bottom line is that a foreign power's military superiority is no match for people who are willing to die to expel that foreign power (assuming the foreign power doesn't resort to eradicating the civilian population).
Unfortunately, this will very likely end the way Vietnam ended for us, where we were flying people off the roof of the US embassy hours before the NVA rolled into town. We'll by flying people out of the Green Zone, weeks or months (if the Iraqi army puts up a fight) before the government is overthrown. And I don't think it makes much of a difference who is President. Obama or Clinton will get us out sooner. McCain will get us out a little later and a little poorer.