Now, it will be necessary to perform a diplomatic miracle. Just as Iran is about to reap the fruits of its nuclear program, America and its allies must convince the mullahs that they would be better off without it. This will require more than the weak sanctions achieved so far. No less than a credible threat of international economic and diplomatic isolation — of making Iran a pariah state — will cause Iran to blink. It’s still worth a try, but time is shorter than we thought.