May to quit as party leader June 7, opening race for new British premier

LONDON— Theresa May ended her failed three-year quest to lead Britain out of the European Union on Friday, announcing that she will step down as Conservative Party leader June 7 and triggering a contest to choose a new prime minister who will try to complete Brexit.

“I have done my best,” May said in a speech outside 10 Downing St., as close aides and her husband Philip looked on, before acknowledging that it was not good enough.

Concluding her remarks, she struggled to contain her emotions and her voice broke as she expressed “enduring gratitude to have had the opportunity to serve the country I love.”

Then she turned and strode through the famous black door of No. 10.

May will stay on as a caretaker prime minister until the new leader is chosen, a process the Conservatives aim to complete by late July. The new party leader will become prime minister without the need for a general election.

She became prime minister the month after the United Kingdom voted in June 2016 to leave the European Union, and her premiership has been consumed by the attempt to deliver on that verdict.

May was brought down by Brexit, but her nemesis wasn’t the EU, with which she successfully struck a divorce deal.

She was felled by her own Conservative Party, which refused to accept it. The plan was defeated three times in Parliament, rejected both by pro-EU opposition lawmakers and by Brexit-supporting Conservatives who thought it kept Britain too closely bound to the bloc.

Many Conservative lawmakers came to see May as an obstacle and blamed her for Britain’s failure to leave the EU on the scheduled date of March 29. The bloc has extended that deadline until Oct. 31 in hope British politicians can break their political deadlock.

The pressure on May reached breaking point this...