Elsewhere, though, Trump does look to be leaving Biden with leverage. The question is how useful it will be. And here four issues suggest its limits. One is whether Trump has left behind the right kind of leverage. Biden made this point earlier this month when he observed that when it comes to leverage over China, "we don't have it yet." The reason tariff concessions aren’t sufficient is that Trump acted unilaterally rather than multilaterally. As Biden wrote back in the spring, “When we join together with fellow democracies, our strength more than doubles. China can’t afford to ignore...