Scarcely a year after a triumphant general-election victory, British Prime Minister David Cameron is already on his way out of office following an epic miscalculation that on Thursday resulted in U.K. voters opting to leave the European Union. Mr. Cameron said Friday morning that he would step down as prime minister within a few months, a consequence of the U.K.’s historic referendum on whether to remain in the EU. Mr. Cameron in effect became collateral damage in a battle he himself launched by promising he would offer the public a vote on the Europe issue if his Conservative Party won the 2015 general election. The referendum’s outcome—nearly 52% of voters cast ballots to leave the EU—instantly reverses the legacy of a man who first became prime minister in 2010 as the leader of a coalition government.
Until early Friday morning, Mr. Cameron had managed to deftly navigate a complex political maze of his own making. Two years ago, he successfully fended off a bid for Scottish independence, and last year he unexpectedly won a general election that gave his Conservative Party its first majority in 23 years.
Before the 2015 election, Mr. Cameron had pledged to hold the referendum on EU membership if his Tories won a majority. The pledge to hold a referendum was a way of mollifying members of his own party, and others, who were unhappy about the U.K.’s membership in the EU.
A Remain vote on Thursday would have completed a tricky electoral trifecta. Instead, Mr. Cameron will be on the hook as the prime minister who paved the way for the U.K. to sever its relationship with the EU—a result that he argued would destroy Britain’s economy and diminish its standing in the world.