Trump’s the one not mentally fit for the presidency

It is unclear whether Donald Trump has forgotten the precise nature of NATO or whether he ever fully grasped it in the first place. What is clear, however, is that Trump — who ostensibly spent four years as president of the United States — has little clue about what NATO is or what NATO does. And when he spoke on the subject at a rally in South Carolina over the weekend, what he said was less a cogent discussion of foreign policy than it was gibberish — the kind of outrageous nonsense that flows without interruption from an empty and…