I didn’t get it when Krauthammer proposed it, I didn’t get it when Hillary proposed it, I don’t get it now.

U.S. President-elect Barack Obama’s administration will offer Israel a “nuclear umbrella” against the threat of a nuclear attack by Iran, a well-placed American source said earlier this week. The source, who is close to the new administration, said the U.S. will declare that an attack on Israel by Tehran would result in a devastating U.S. nuclear response against Iran…

A senior Bush administration source said that the proposal for an American nuclear umbrella for Israel was ridiculous and lacked credibility. “Who will convince the citizen in Kansas that the U.S. needs to get mixed up in a nuclear war because Haifa was bombed? And what is the point of an American response, after Israel’s cities are destroyed in an Iranian nuclear strike?”

The current debate is taking place in light of the Military Intelligence assessment that Iran has passed beyond the point of no return, and has mastered the technology of uranium enrichment. The decision to proceed toward the development of nuclear arms is now purely a matter for Iran’s leaders to decide. Intelligence assessments, however, suggest that the Iranians are trying to first accumulate larger quantities of fissile material, and this offers a window of opportunity for a last-ditch diplomatic effort to prevent an Iranian bomb.

I made this point in the posts linked up top: How is this policy preferable to helping Israel boost its second-strike capabilities? It already has enough firepower to “completely and utterly obliterate” Iran. Outfit its submarines with nuclear CBMs, upgrade its defensive anti-ballistic missile systems, and and let it take care of business. The “umbrella” route only really makes sense for countries with no weapons, to deter regional nuclear powers from bullying them and to deter those under the umbrella from being spooked into building nukes of their own. That’s why Hillary’s idea to extend the policy to Saudi Arabia makes a certain perverse sense — or would, if you could find an American eager to jump into a nuclear war to defend Riyadh. The umbrella policy could, I guess, in theory be an incentive to get Israel to give up its own weapons and set a “non-nuclear” standard for the Middle East, but given the vicissitudes of American politics and, as Richard Fernandez says, the fact that there’s no reason to believe the west would act to nuke Iran when it wasn’t willing to stop Iran from getting nukes in the first place, the Israelis would be insane to agree to that.

All of this is premised upon the assumption that assured destruction would be enough to deter Iran from trying to decapitate Israel in the first place. Obama’s a lot more confident of that than I am. In case you’re curious about our new secretary of state’s thoughts on the subject, here’s a clip of her rambling on about it from Olbermann’s show in April. Skip ahead to 5:35. Exit question one: Is The One prepared to bring Arab countries under the umbrella too? If not, how will that affect the image he’s trying to build as an honest broker between Israel and Muslims? Exit question two: He’s said repeatedly that Iranian nukes are “unacceptable,” but of course Bush has been saying that for years and did nothing to stop them. Doesn’t this policy signal that The One’s preparing to accept the fact of Iranian nukes after all?