The wedge issue of the 2016 primary campaign is the rising hostility to free trade—and, specifically, to the Trans-Pacific Partnership. On the Republican side, establishment candidates like Jeb Bush, Scott Walker, and Marco Rubio have failed or fallen behind, while Donald Trump maintains a commanding lead going into Florida and Ohio thanks, in large part, to his protectionist rhetoric. On the Democratic side, Hillary Clinton has been veering leftward to fight off a determined challenge from Vermont’s democratic socialist Bernie Sanders, another unapologetic protectionist.