Today, the control rods are being lifted. With each racist assault — on a judge, an athlete, a country, a member of Congress, or a city — and with each kind word for “very fine people on both sides,” our president allows the stew to boil and radiate more dangerously.

You can feel the effect: in the F.B.I.’s burgeoning caseload of hate crimes and white supremacist investigations, and in a stadium full of Americans who, even knowing they are on television, chant in unison, “Send her back.” That burst of negative energy was met, not by efforts to control it, but by 13 seconds of presidential silence, the same silence that his fellow Republicans have adopted.

Our president thinks he is doing something clever. He lifts the control rods for a calculated and deeply cynical purpose: to harness the political energy unleashed. It will heat his re-election bid, he likely thinks. But unconstrained, it will damage the nation, in all directions. Only fools believe they can ride the gamma rays of hate.