(Bloomberg) -- U.K. and European Union negotiators have reached a Brexit withdrawal deal. But the saga is far from over. Prime Minister Theresa May’s opponents in Parliament have mobilized against her in an effort to thwart the agreement. She risks being overthrown, and even if she clings on, it’s hard to see how she’ll win the necessary approval from Parliament, where she doesn’t have a majority and faces opposition on all sides. Here’s a guide to navigating the most perilous part of Brexit.

1. Why could Brexit cost May her job?

Pro-Brexit lawmakers from her Conservative Party hate the deal and are trying to engineer a no-confidence vote in her as party leader. If 48 Tory lawmakers send in letters of no-confidence, a vote will be held. They need a larger number -- 158 -- to win it. Many Tories are hesitant to undermine the prime minister with Jeremy Corbyn’s socialist Labour Party itching to take power. If she survives then she’s safe for a year.

2. Could we end up with an election?

Conceivably, yes. British law in theory says that elections are only held every five years. But May called an early poll in 2017, and if her deal is voted down in Parliament then many lawmakers reckon the most logical next step is an early general election. That could be triggered by a vote of no confidence in the government, or if two-thirds of the chamber vote for one.

3. What sort of deal did May strike with the EU?

The deal -- the most important international agreement in Britain’s postwar history -- sets out the terms of separation that allow the U.K. to depart the EU on March 29 in an orderly fashion. It brings with it a 21-month grace period to give everyone time to adjust. The pact comes with a political declaration that sets out how the two sides want to trade in the future, though the details of a free-trade deal could take years to work out.

4. What’s the problem with the deal?

There’s a furious group of pro-Brexit Tory lawmakers who think May’s caved to the EU and betrayed the electorate’s call to regain sovereignty. Some anti-Brexit ministers are also worried that the deal traps the U.K. in a customs union with the EU indefinitely, leaving it beholden to too many of the EU’s rules. It’s looking extremely difficult for her to get Parliament’s approval -- the Labour Party has rejected it, as have Tories on both sides of the debate. And the 10 Northern Irish lawmakers who prop up her government are also signaling they will vote against because the deal treats the territory differently to the rest of the U.K.

5. What happens if Parliament votes the deal down?

Depends who you ask. If Parliament rejects it, Labour will push for a general election and a chance to govern. But the chaos that ensues would probably also provide the best opportunity for lawmakers to trigger a second referendum in the hope of reversing Brexit. A cross-party group is trying to engineer a re-run of the June 2016 vote on leaving the EU but so far there’s nowhere near a majority for it. There’s a real chance that if the deal is voted down, the country would crash out of the bloc into a legal limbo that would snarl trade and freeze up markets.

6. So when will Parliament vote?

It’s the question on everyone’s lips -- especially traders’. The expectation is sometime in December, after a special EU summit on Nov. 25. But for that to happen, May has to survive for another couple of weeks. Lawmakers expect early December, before Parliament goes into recess on Dec. 20.

The Reference Shelf

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