LONDON, (DNA) – Parliament was set for a historic vote Tuesday as British Prime Minister Theresa May lobbied for support but braced for defeat of the U.K.’s divorce deal with the European Union.

Lawmakers finally get their chance to say yes or no to May’s deal after more than two years of political upheaval. All signs indicate a resounding rejection, despite pleas from May and her allies on the final day of debate.

Attorney General Geoffrey Cox told lawmakers in the House of Commons it would be “height of irresponsibility” to reject the agreement and plunge the country into uncertainty.

“You are not children in the playground — you are legislators,” he said. “We are playing with people’s lives.”

A “no” vote would mean further turmoil for British politics only 10 weeks before the country is due to leave the EU on March 29. It is not clear if it would push the government toward an abrupt “no-deal” break with the EU, nudge it toward a softer departure, trigger a new election or pave the way for a second referendum that could reverse Britain’s decision to leave.

May, who leads a fragile Conservative minority government, has made delivering Brexit her main task since taking office in 2016 in the wake of the country’s decision to leave the EU.

Despite a last-ditch plea from the prime minister for legislators to give the deal “a second look,” it faces deep opposition from both sides of the divide over U.K.’s place in the bloc. Pro-Brexit lawmakers say the deal will leave Britain bound indefinitely to EU rules, while pro-EU politicians favor an even closer economic relationship with Europe.

That leaves the agreement facing likely defeat on a day of political drama brimming with a very British mix of high drama, low insults and convoluted parliamentary procedure.

The government and opposition parties ordered lawmakers to cancel all other plans to be on hand for the crucial vote. One Labour legislator, Tulip Siddiq, delayed the scheduled cesarean birth of her son so she could attend.

As lawmakers debated in the House of Commons chamber, outside there was a cacophony of chants, drums and music from rival bands of pro-EU and pro-Brexit protesters. One group waved blue-and-yellow EU flags, the other brandished “Leave Means Leave” placards.

Lawmakers were scheduled to vote Tuesday evening, after the last of five days of debate on the deal struck between May’s government and the EU in November.

May postponed a vote on the deal in December to avoid certain defeat, and there are few signs sentiment has changed significantly since then.

Before the main vote, lawmakers will decide the fate of four amendments that reflect the huge range of opinion among lawmakers about how Britain should pursue Brexit. One amendment from the Labour Party rejects May’s deal and also rules out leaving the bloc without agreement, while one from the Scottish National Party seeks to postpone Britain’s departure from the EU.

Two others seek to limit the deal’s most contentious section, an insurance policy known as the “backstop” that is designed to prevent the reintroduction of border controls between the U.K.’s Northern Ireland and EU member Ireland.

Assurances from EU leaders that the backstop is intended as a temporary measure of last resort have failed to win over many British skeptics, and the EU is adamant that it will not renegotiate the 585-page withdrawal agreement.

Arlene Foster, who leads Northern Ireland’s Democratic Unionist Party — May’s parliamentary ally — said her party would vote against the deal because of the backstop.

“We want the PM to go back to the EU and say ‘the backstop must go,’” Foster said.

In a sign of the widespread opposition, Parliament’s unelected upper chamber, the House of Lords, voted 321-152 late Monday in favor of a motion saying May’s deal would damage Britain’s economic prosperity, internal security and global influence, while also rejecting the idea of leaving the EU without a deal. That vote has no direct effect on the fate of May’s deal.

May says rejecting the agreement would lead either to a reversal of Brexit — overturning voters’ decision in the 2016 referendum — or to Britain leaving the bloc without a deal. Economists warn that an abrupt break from the EU could batter the British economy and bring chaotic scenes at borders, ports and airports.

Business groups appealed for lawmakers to back the deal to provide certainty about the future.

Mike Hawes, chief executive of the Society of Motor Manufacturers and Traders, said parliamentarians “hold the future of the British automotive industry — and the hundreds and thousands of jobs it supports — in their hands.”

“Brexit is already causing us damage in output, costs and jobs, but this does not compare with the catastrophic consequences of being cut adrift from our biggest trading partner overnight,” he said.

If Parliament votes down the deal, May has until Monday to come up with a new proposal. So far, May has refused publicly to speculate on a possible “Plan B.”