If that happens Israel will make the assumption that Iran did it. They will remove Iran as a functioning society. I would expect nuclear hits on their major military bases, and population centers. Israel can absorb a first strike(albeit with tremendous damage and loss of life) and still strike back. To destroy Israels capability to strike back it would be necessary to take out their entire Air Force, Missile Force, and their subs. That will not happen. Nor would it surprise me for them to take out Pakistan's nuclear facilities as an act of revenge, The current spread of nuclear weapons is a result of Khan of Pakistan. He sold nuclear technology to Libya, Syria, North Korea, and Iran.
If they do abosorb a first strike their retaliation capabilities will be severely limited... maybe they get on back on Tehran however, Iran doesn't care in the mind of Amadmannajad Israel will be gone... don't be too suprised if the terrorists get on in Manhatten too just to prove the point that the President has been making the oceans do not protect us from this threat.... Anyway the bottom line is that after NOV election this president will be stripped of any command authority... censure, impeachment, executive power limits, the liberals wedge issue deployment very well may win them majorities...