The controversy du jour is John McCain's comment this morning that it's "not too important" when American troops come home. McCain's campaign is hitting back on this, and it's certainly true that McCain proceeds to say that what matters is whether American troops are taking casualties. But I think McCain's comment, like his "100 years" commment, is an important and legitimate thing for Obama to focus on for two reasons:

1. McCain's goal of turning Iraq into a place where American soldiers can stay peacefully, like West Germany or South Korea, is wildly unrealistic. I won't say it's impossible, because anything is possible. But the history of the Middle East suggests that Iraqis are never going to accept a long-term American military presence. Indeed, even if you thought Iraqis would welcome American troops as liberators, which was optimistic but not totally crazy, it would take a whole different level of delusional optimism to think that they'd also welcome scores of permanent U.S. bases in the country. So these comments are a window into McCain's rosy scenario that ought to be challenged.

2. McCain will never say how long he's willing to fight on in order to get to this casualty-free scenario he envisions. Yes, he wants the Iraq occupation to become like the West German occupation, but right now it's not, and McCain won't concede there's any limit to how long the status quo is acceptable to him. He repeatedly turns questions about how long the current war can go on into postulates about a hypothetical future peaceful occupation. It's not the same thing as saying he's willing to keep taking casualties for 100 years, but it is the answer he gives to that question, and as such it's highly suggestive.

--Jonathan Chait