"Every man, woman and child lives under a nuclear sword of Damocles, hanging by the slenderest of threads, capable of being cut at any moment by accident or miscalculation or by madness,” the American president told the world, friend and foe alike.

That was John F. Kennedy, speaking to the United Nations in 1961, in one of his many public entreaties to America’s adversaries and all humankind to limit the insanity of atomic warfare. His predecessor had started seizing the high ground in the nuclear age with bold ideas for controlling these diabolical weapons, and other presidents would continue, in time leading to arms-control and test-ban treaties and helping (so far) to avert nuclear holocaust.

Joe Biden also used to speak regularly and urgently about the dangers of nuclear proliferation and war. But that was when he was vice president and apparently moving toward endorsing an official U.S. policy of "no first use,” a doctrine to which only China among the world’s nine atomic powers subscribes today. Since becoming president, though, Biden has largely been silent on the subject. So has his vice president and possible successor, Kamala Harris.