The Obama administration, like so many well-intentioned Western journalists and scholars, locked onto this hope for gradual transformation from theocracy to democracy even though within Iran it had been shattered. The death of this dream was the electoral triumph in 2013 of Mr. Rouhani, a founding father of the regime’s dreaded Intelligence Ministry. Iranians, who would surely down theocracy in a free vote, have a political system that gives them the option of voting for Mr. Rouhani or even more distasteful candidates.

Many Americans still want to believe that the Islamic Republic can peacefully evolve into something less malign. After all, American foreign policy is much more difficult if Iran remains an aggressive theocracy. The nuclear deal seems less astute if, when the sunset clauses kick in and the atomic restrictions start coming off in six years, Iran has tens of thousands of loyal Shiite militiamen spread across the Middle East and has increased the capacity of its long-range ballistic missiles.