On Tuesday, the U.K. parliament will be tasked with approving the terms of Theresa May’s deal to transition the country out of the European Union and have it exist as its own economic entity.

On one side of the bargain are May and the European Union, who forged a deal earlier this year that was dubbed a “soft Brexit.” In this deal, the U.K. and EU would enter into a transition period that would allow it to operate within the EU as if it were still a member nation until 2020. May hoped this would allow businesses owned and operating in the U.K. to prepare for the eventual break, while providing the parliament more time to develop a series of regulations and customs regarding imports and exports that, until now, have been determined by the EU. After successfully striking a deal with the EU, May faced difficulties from members of her own political party who said the deal was too forgiving to the EU, and also took grievance with an agreement between May’s government and the EU that would effectively keep the border between Northern Ireland (which is part of the U.K.) and the Republic Ireland to remain open.

The “Irish backstop” has taken prominence in the split between conservatives and May, and was one of the issues that caused May to delay a vote last month on her Brexit deal, for fear it would fail. On Monday, May urged members of her own party to reconsider the agreement and asked them to approve her deal.

“It is not perfect, but when the history books are written, people will look at the decision of this House tomorrow and ask, 'Did we deliver on the country's vote to leave the EU, did we safeguard our economy, security or union? Or did we let the British people down?'” May said.

Despite her pleas, analysts say that without any substantive change, May’s deal and her legacy will most likely be voted down tomorrow.

“I don’t see any major changes in the proposal, so I presume she could lose it here,” said WGBH News Analyst and CEO of the GroundTruth Project Charlie Sennott. “She’s tried to thread the needle through the middle, and it’s not clear that her own party is going to accept that. Cabinet ministers are just pushing for the May deal to be defeated, and to re-do the deal.”

Under the terms of the current Brexit agreement, the U.K.’s exit from the EU is slated to happen in March 2019 with or without a deal. Currently, neither side seems to be budging from their positions on the Irish backstop. Despite assurances from EU President Donald Tusk and European Commission President Jean Claude Juncker that the EU respects the U.K.’s decision to leave the EU and the current terms of the withdrawal agreement are only temporary solutions until a formal agreement can be arranged, conservatives in the U.K. parliament don’t appear to be convinced. On Monday, Gareth Johnson, a minister of parliament and the whip of May’s Tory Party, resigned in protest of May’s deal and the upcoming vote, and an analysis by "The Guardian" says more than 200 MPs are expected to vote against May’s deal.

“Like you, I am not only a Conservative but I am also a committed Unionist and I cannot accept the additional regulatory compliance required of Northern Ireland that would set it apart from the rest of the United Kingdom,” Johnson said in an open letter posted to social media.

Should a vote fail tomorrow, the question will then turn to how the U.K. should brace itself for a hard break with the EU, which will completely remove the U.K. from the EU’s economic trading zone, of which its been a member since the union’s inception. The move could not just dramatically alter the U.K.’s economy, but also the global economy where investors are skittishly watching what happens to determine whether they should begin pulling their money out of the U.K.’s market. For now, Sennott says the only thing people can do is wait and see what happens.

“The question at the end of the day is going to be: Did May pull this off, can she hold this together, can she win the confidence of the parliament to get this thing through, or are they going to reject it?” Sennott said. “Otherwise it’s going to be a hard exit, and that’s going to be really bad for the U.K.’s economy, and that’s going to be really bad for the world’s economy.”