And they add that since the agreement permanently enjoins the Iranians from acquiring nuclear weapons, the United States maintains the military option to stop them from doing so.

Yet Iran’s regional behavior has become worse since the nuclear deal came into effect, not least because it provided the regime with a huge new income stream — $10 billion in cash and gold in 2016 alone, plus more than $100 billion in additional sanctions relief — to fund its work. Tehran also operates on the assumption, well justified during the Obama years, that the United States would not risk the nuclear deal for the sake of rolling back Iranian gains in Syria and elsewhere.

As for the point that the Iranians are generally (if not quite entirely) honoring their end of the bargain — why shouldn’t they? “Iran doesn’t want a bomb today,” one senior Israeli official told me. “It wants a bomb tomorrow.” That is, it wants a robust nuclear base that puts it within a screw’s twist of a sizable nuclear arsenal without the economic and security risks of actual possession.

And if it does choose to go for a bomb once the agreement has run its course, our military options will be slight. If we couldn’t prevent Pakistan or North Korea from going nuclear in the 1990s, why should we think we’ll be able to stop Iran in the nick of time?

My critics will claim that a distant prospect of a nuclear Iran is still vastly preferable to an exit from the deal that allows Iran to bring its centrifuges out of storage and start spinning its way to a bomb once again, this time without the monitoring of United Nations inspectors.

Maybe. But Iran still wants the economic benefits of the deal — benefits Washington alone can bestow through waivers, permits, relief from secondary sanctions and control over dollar transactions. The American Goliath needn’t be helpless against a Middle Eastern state with a gross domestic product only slightly larger than that of metropolitan Atlanta.

We are living through a nuclear nightmare on the Korean Peninsula after more than two decades of optimistic diplomacy. That’s a fate we ought to do everything possible to avoid with Iran. As Mark Dubowitz of the Foundation for Defense of Democracies points out, “decertification isn’t a sufficient condition to break the paralysis of our Iran policy, but it is a necessary one.”

Even if the rest of the difficult enterprise rests in the hands of — God help us — President Trump.