Once upon a time, when choosing a new president, a factor for many voters was the perennial question: “Whose finger do you want on the nuclear button?” Of all the responsibilities of America’s top executive, none may be more momentous than deciding whether, and under what circumstances, to activate the “nuclear codes” — the secret alphanumeric messages that would inform missile officers in silos and submarines that the fearful moment had finally arrived to launch their intercontinental ballistic missiles (ICBMs) toward a foreign adversary, igniting a thermonuclear war.