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– British lawmakers on Tuesday rose up against Prime Minister Boris Johnson, moving to prevent him from taking the country out of the European Union without a formal agreement, and precipitating an epic showdown that could provoke a snap general election.

The lawmakers voted to take control of Parliament away from the government, giving themselves the authority to pass legislation that would stop the prime minister from his threat of a no-deal Brexit.

It was a critical moment in Britain's tortured, three-year effort to extract itself from the European Union. The saga has divided Britons, torn apart the ruling Conservative Party and prompted complaints that Johnson has trampled the conventions of the country's unwritten constitution.

A majority of lawmakers are determined to block leaving the European Union without a deal, which they believe would be disastrous for the country's economy. Tuesday's vote suggested they have the numbers to succeed.

Johnson's aides had made it clear that, in the event of a defeat on Tuesday, he would seek a general election on Oct. 14 — just a little more than two weeks until the Brexit deadline of Oct. 31 — though Parliament would have to agree to that.

The accelerating pace of events suggests that Britain's Brexit nightmare may finally be approaching an endgame after years of paralysis.

Tuesday's vote also marked the moment when Johnson's hardball tactics, for once, were met with equal resistance.

On a day of high drama, Johnson lost his working majority in Parliament even before the vote took place, when one Conservative rebel, Phillip Lee, quit the party to join the Liberal Democrats, who have managed to stage a resurgence by positioning themselves as an unambiguously anti-Brexit party.

The practical effect of Lee's defection for Johnson was limited, however, because the government would fall only if it were defeated in a confidence motion.

But in a symbolic moment, Lee walked across the floor of the House of Commons and sat beside Jo Swinson, the leader of the Liberal Democrats, as Johnson was speaking about the recent summit of the Group of 7 leaders. Lee accused Johnson of pursuing a damaging withdrawal from the European Union in unprincipled ways, and of "putting lives and livelihoods at risk."

Lee's departure from the Tories may not be the last; Johnson has promised to expel any Conservative lawmaker who voted against him on Tuesday. That could threaten his ability to manage day-to-day business in Parliament, underscoring the need for a new election.

The extent of the Tory civil war was on full display as several of Johnson's Conservative critics lobbed hostile questions at him, making it plain that they had not been brought back into line by threats of expulsion from the party.

Opponents of a no-deal Brexit argue that Johnson's promise to leave the bloc without a deal, if necessary, would be catastrophic for the British economy. Many experts say it could lead to shortages of food, fuel and medicine, and wreak havoc on parts of the manufacturing sector that rely on the seamless flow of goods across the English Channel. Leaked government reports paint a bleak picture of what it might look like.

Johnson says he needs to keep the no-deal option on the table to give him leverage in talks in Brussels, because an abrupt exit would also damage continental economies, if not as much as Britain's.

To add to the turmoil and confusion, the opposition Labour Party suggested it might thwart Johnson's attempt to push for a general election, should it come to that. Under a 2011 law, the prime minister needs a two-thirds majority to secure a snap election, although it is possible that the government might try to legislate to set that provision aside, a move that would mean it needs only a simple majority.

There is so little trust in British politics that Johnson's opponents fear that he might request an election for Oct. 14 but then switch the date until after Oct. 31 as part of a move to lock in a no-deal withdrawal.

Labour has said that its priority is to stop Britain leaving the European Union without a deal because of concerns about what such a departure would mean for the economy.

But Labour's stance underscores that the backdrop to everything in British politics is a sense that a general election is looming, with key players maneuvering for the most advantageous moment.