London — British Prime Minister Theresa May faced the prospect of defeat in a historic vote in parliament on her Brexit deal on Tuesday, leaving the country in limbo about its membership of the world's biggest trading bloc, which has shaped its economy for decades. May urged legislators on Monday to take a second look at her deal but parliament appeared set to reject the agreement in a voting session due to start at 7pm GMT. May's hopes of saving the plan will hinge on the scale of her loss: if she limits the size of the expected defeat, May will probably ask Brussels for more concessions in the hope of getting her plan through parliament in another vote. But a humiliating outcome could force May to delay Britain's scheduled departure from the EU on March 29 and potentially open up other options ranging from a second referendum to leaving the EU with no deal. Dominic Raab, who resigned as May's Brexit minister in November in protest at her plans, said it was time to prepare for a no...