The (Ex) Washington Realist

I think that you are incorrect in singling out Iran's issue. In fact, Mr. Obama's administration has not made any substantive changes (qualitative changes) in the relationship between US and Russia, Cuba, Venezuela, North Korea, PA, Syria, and Iran. Nothing has changed over the last 12 months except, perhaps, the atmospherics.

In the specific case of Iran; that country had requested, publicly and privately, that improvement of her relationship with US is contingent upon the US being willing to dismantle, through a published Framework, her cold war against Iran. What the Iranian government has been told is that the President of the United States, because of domestic issues and politics, cannot move in that direction.
 

On a nuclear Iran:

- Possession of nuclear warheads by a state does not by itself deter external attack. This was the reason why conventional power balances mattered so much during the Cold War. I would agree that an Iranian nuclear arsenal makes a discretionary attack by an outside power less likely but in a crisis an adversary could still launch a conventional strike. The mullahs would then have to decide whether to make first use of nuclear weapons. Whether they would be willing to do so, knowing the certainty of retaliation, is hardly clear.

North Korea is not really comparable to Iran because it has both the protection of China and (presumably) the restraining influence of Beijing.

- Israel would certainly be less secure with a nuclear Iran but you also need to take into account the impact on the Arabs. It appears that the moderate Arab governments have been toning down their differences with Israel as a result of Iran's impending capability, and the moderate Arabs may go nuclear if Iran does so. The real danger to Israel is likely to be the scale and extent of proliferation, a prospect that threatens everyone in the region, to say nothing of the outside world if recent estimates of the environmental effects of a local nuclear war are true.

- I agree that after crossing the nuclear weapons threshhold Iran could export the technology (or even export ready-to-launch missiles capable of delivering nuclear warheads) to other countries. Venezuela under its current leader would be an obvious candidate to receive them.

- The prospect that a change of regime in Iran would do little to change that country's nuclear program or tensions with its neighbors may confirm the view (expressed by Henry Kissinger a few years ago) that nuclear proliferation is a threat to the international system itself. There needs to be a realist answer to a system-level threat if that is what we face.
 

David Billington:

In fact there is concerted effort by Saudi Arabia, Turkey, Iran, Syria, Qatar, Azerbaijan, and Oman to cooperate in spite of US/EU/NATO strategies (some would say fantasies) to isolate Iran.

These other states may not like Iran but they have business that they have to conduct and then cannot wait for another 8 years to have the fantasies of Washington to bear fruit.