"... It could very well be that we can no longer -- and could never -- do anything to stop that from happening ..."

Judah Grunstein in WPR/ here

" ... None of this represents a failure of the Obama administration's policy of engagement, which was complicated by an Iranian political crisis that continues to limit Tehran's ability to take yes for an answer. Absent an opportunistic -- but also revealing -- Green movement attack on the deal, it might have gone through (although that's impossible to say for sure).

Given some of the dramatically incoherent declarations coming out of Tehran over the past few weeks, it's also still possible that a last-minute deal is in the works. There's even a diplomatic trail for backchannel negotiations, with a Qatari crown prince making a Tehran-Paris shuttle run last week, followed by an announced trip by Secretary of State Hillary Clinton to Qatar this weekend.

In the meantime, the case for sanctions, both at the U.N. and unilaterally, has been enormously strengthened ..... Will sanctions prove effective? Probably not, although the sanctions being described -- which target the Revolutionary Guard in order to reinforce the faultlines in the Iranian regime -- seem to be more thoughtfully conceived than previous rounds.

Is a nuclear -- or a latent-nuclear -- Iran the end of the world? Probably not, although it would come with great many consequences, many of them unpredictable and most of them unwelcome.

It could very well be that we can no longer -- and could never -- do anything to stop that from happening. But sometimes diplomacy is as much about second-order effects as immediate results. The inability to block Iran's nuclear ambitions reveals the limits of American power when it is not supported by other poles of influence in the increasingly diffuse global balance of pwoer. But by positioning the U.S. to be not only right, but reasonable, the Obama policy will enhance our subsequent ability to mobilize regional and global pressure in similar situations."