Why do it? It seems clear that Trump disdains the Iran nuclear deal, at least in part, because it is a signature accomplishment of the Obama presidency — a legacy perhaps second only to the Affordable Care Act in its symbolic significance. That helps explain why the president has described the deal as an “embarrassment” and “the worst deal ever,” hyperbole that has only made it more difficult for him to regularly report to Congress that Iran is actually doing its part.
The president prefers to wash his hands of the deal and let Congress decide its fate. Refusing to confirm Iran’s compliance while laying out a broad case against Iran will, in effect, invite Congress to impose new sanctions. But if other signatories to the deal side with Iran in declaring the United States in violation and resist U.S. pressure to curtail their business dealings with Iran, all that “decertification” will achieve will be to open a rift between the United States and its European allies, Russia and China. On the other hand, if the United States wins over its allies, the deal will be dead — and everyone can go back to worrying about war with a nuclear-armed Iran. [...]
That constituency gave President Hassan Rouhani a resounding victory and a clear mandate in the presidential election in May. Rouhani ran a campaign built on the success of the nuclear deal and the promise of the opening to the West. In August, an overwhelming majority in the Iranian parliament — cutting across reformist and conservative party lines — voted to reconfirm Foreign Minister Mohammad Javad Zarif, the chief negotiator of the nuclear deal on the Iranian side. The deal has increasingly redrawn political battle lines in Iran along whether to invest the country’s future in engagement with the United States.
