Alright, well that overstates the case a little bit. But thanks to the general trend of developments in Iraq (where Obama is getting very favorable press now), and some comments over the weekend by Nouri al-Maliki that seem to suggest he's generally on board with Obama's withdrawal plan, it is becoming increasingly difficult for McCain to argue that we must be prepared to permanently occupy Iraq. Thus, it is becoming increasingly difficult for him to distinguish himself from Obama on Iraq and consequently, Iraq is becoming less and less of an issue in the general campaign. In fact, contemplate Obama's highly favorable position for a moment: if the situation in Iraq were to worsen, it's possible to argue that the surge was a failure and that withdrawal is now our only option. If the situation in Iraq remains stable, Obama can argue that our troops have achieved their objective and that it's time to begin bringing them home (or sending them to Afghanistan) and...oh yeah, the Iraqis agree! In these circumstances, what can McCain do to distinguish himself from Obama? Argue that our troops should be prepared to stay however long it's necessary, and just ignore the signals Maliki is giving that the Iraqis might favor us leaving? Argue that things are worse than they seem, thus undermining the apparent "success" of the surge and the Awakenings movement? Keep talking about bombing Iran? The right senses this quandary too, and are of course frustrated that Obama could put himself in position to reap either the fruits of the success or the failure of the surge.
It's possible (not likely or certain, but simply possible) that Obama could soon be in a position to negate the usefulness of Iraq to the Republicans altogether. With that issue marginalized, Obama can turn his attention to hot spots like Afghanistan or domestic issues like the economy, where McCain is struggling. And with McCain disarmed of his primary weapon, his position on Iraq, the road to the White House begins to look considerably more difficult for him.
UPDATE: Maliki reaffirms his commitment to have American troops out of Iraq by the end of 2010. It's impossible to argue that Maliki is not on the same page with Obama at this point.