The shocked reactions of many European leaders suggested they had not fully absorbed the possibility of a vote for Brexit. Angela Merkel, Germany’s chancellor, called a crisis meeting of parliamentary leaders and cabinet members. In Rome, the Italian prime minister, Matteo Renzi, convened an emergency meeting of ministers and scrapped a scheduled summit of his party’s leaders. France’s president, François Hollande, held a long emergency session at the Elysée. When he emerged his tone was measured (he promised to continue to work closely with Britain), but he added that the EU now needed a “leap forward” to ward off the...