Indeed, according to a source close to the discussions, the action that participants currently see as most likely is a joint U.S.-Israeli surgical strike targeting Iranian enrichment facilities. The strike might take only "a couple of hours" in the best case and only would involve a "day or two" overall, the source said, and would be conducted by air, using primarily bombers and drone support. Advocates for this approach argue that not only is it likely to be more politically palatable in the United States but, were it to be successful -- meaning knocking out enrichment facilities, setting the Iranian nuclear program back many years, and doing so without civilian casualties -- it would have regionwide benefits. One advocate asserts it would have a "transformative outcome: saving Iraq, Syria, Lebanon, reanimating the peace process, securing the Gulf, sending an unequivocal message to Russia and China, and assuring American ascendancy in the region for a decade to come."
While this approach would limit the negative costs associated with more protracted interventions, it could not be conducted by the Israelis acting alone. To get to buried Iranian facilities, such as the enrichment plant at Fordow, would require bunker-busting munitions on a scale that no Israeli plane is capable of delivering. The mission, therefore, must involve the United States, whether acting alone or in concert with the Israelis and others.
What does this have to do with Romney's remarks? Were it clearer that the primary Iran option being discussed is this very limited surgical strike, then a U.S. threat of force would be that much more credible. And if it were more credible -- because it seemed like the kind of risk the president is more willing to undertake -- then it would have the added benefit of providing precisely the kind of added leverage that might make diplomacy more successful. In other words, the public contemplation of a more limited, doable mission provides more leverage than the threat of even more robust action that is less likely to happen.
With that in mind, and given the progress that the Israelis and the administration seem to have made in the past couple of weeks, it may be that the easiest way for the Obama team to defuse Romney's critique on Iran is simply to communicate better what options they are in fact considering. It's not the size of the threatened attack, but the likelihood that it will actually be made, that makes a military threat a useful diplomatic tool. And perhaps a political one, too.