Tony Karon writes: A used car salesman, a Mexican narco snitch, and an Iranian spook walk into a bar. What is this, says the ex-CIA barman, some kind of a joke?

Let’s just say that the ostensibly Iranian plot to blow up Saudi Arabia’s ambassador to Washington is not yet proving to be the smoking gun that allows the Obama Administration to rally uncommitted governments to the cause of isolating Tehran. Sure, the Saudis have brought the matter to the attention of the U.N. Security Council, although they have not as yet indicated that they intend to call for any specific response. But with skepticism rife even in Washington about this plot having been authorized by the Iranian leadership, the narco-proxy terror scheme may not change the minds of Russia, China, Turkey and other opponents of any new sanctions. After being briefed on the plot by U.S. diplomats, those countries and others have said they want more information before making up their minds — as have the Iranians, although Tehran has also tossed out a curveball by suggesting that the fugitive accused in the case is, in fact, an operative of the Mujahedeen e-Khalq, an exiled opposition group currently listed as a terrorist organization by the U.S. State Department.

But the Administration is reportedly unlikely to provide further evidence, for fear of compromising sources and methods.

So, as things stand, the Saudi ambassador plot looks unlikely to be a game-changer. Of course, the same hawkish crowd in Washington that agitated for the Iraq invasion are demanding military action against Iran, but despite President Obama’s tough talk last week about imposing “the toughest sanctions” and keeping the proverbial “all options” on the table, it’s the five-year nuclear stalemate, rather than the alleged assassination plot, that will frame the international response to Iran.