Democrats have been debating whether to tolerate congressional candidates who are pro-life, but when it comes to economic issues party leaders seem to have decided they’re all Sandernistas now. For example, there is absolute unanimity among senior elected Democrats in Washington that government should dictate a higher minimum wage. But this is another issue that deserves debate. New research shows the damage that minimum-wage laws have done to U.S. workers—and not just those employed in restaurants.

The latest warning against...