Donald Trump Effectively Just Told Iran to Get a Nuclear Weapon

Anyone can get distracted now and then, and say things out loud he or she probably shouldn’t say. Perhaps an excited friend lets on about a surprise party, or a co-worker dishes up some unseemly office gossip. Or, if you’re the president of the United States, you might reveal some numbers about an adversary’s nuclear arsenal and then admit that those weapons, even a relatively small number of them, are pretty darn useful. Donald Trump made this impromptu foray into nuclear-deterrence issues…