If ever there was evidence that voters took a big risk by electing President Trump, this tweet last Friday was it: “Trade wars are good, and easy to win.”

The day before, on March 1, Trump had announced he would soon impose massive tariffs on foreign steel and aluminum imports. This is a gut-punch for American manufacturers that use steel. Trump’s devil-may-care attitude toward an economically destructive act is unnerving and adds insult to what will be serious economic injury.