Can Brexit Be Stopped?

BOURNEMOUTH, England—Standing onstage in front of her party faithful, Jo Swinson had a surprise. At the opening rally of the Liberal Democrats’ conference here at the British seaside, the crowd knew what to expect—all week, rumors had been buzzing that they would be joined by a high-profile defector from a rival party—but they didn’t know whom to expect. Swinson, the party’s newly elected 39-year-old leader, said the person she was introducing was “someone who has stood up for liberal values,” and moments later, Sam Gyimah bounded up onstage.