Shawn Fain, president of United Auto Workers, took to social media Thursday to give a policy speech. "There's a lot of uncertainty over what this moment holds," he said.

Donald Trump’s ambitious yet erratic announcements on tariffs have roiled financial markets and provoked a flurry of panicked commentary in the media. But qualified support for Trump’s trade policy has come from what is in some ways an unexpected corner — the United Auto Workers (UAW),