President Trump said Monday that he’d meet Iranian President Hassan Rouhani with “no preconditions,” and after meetings with Kim Jong Un and Vladimir Putin this was probably only a matter of time. Mr. Trump has preternatural confidence in his negotiating ability—and every other ability. But give Mr. Trump credit for noticing at the same time that Iran’s regime is “having a hard time right now,” for which he can take some credit.

Tehran is struggling to control capital flight as Iranians anticipate the reimposition of U.S....