Iran's nuclear threat was never in doubt during its presidential campaign, but the post-election resistance raised the possibility of some sort of regime change. That prospect seems lost for the near future or for at least as long as it will take Iran to finalize a deliverable nuclear weapons capability.
Accordingly, with no other timely option, the already compelling logic for an Israeli strike is nearly inexorable. Israel is undoubtedly ratcheting forward its decision-making process....With regime change off the table for the coming critical period in Iran's nuclear program, Israel's decision on using force is both easier and more urgent. Since there is no likelihood that diplomacy will start or finish in time, or even progress far enough to make any real difference, there is no point waiting for negotiations to play out. (John R. Bolton in WaPo)
Here's the best bit: