Theresa May's Brexit deal is scheduled, despite the expected defeat, to be put before the UK parliament on Tuesday evening.
The British prime minister is fighting to persuade a majority of MPs in the 650-strong House of Commons to back the agreement she struck with the EU after over 20 months of negotiations.
A victory against the odds can't be discounted, but with almost all opposition MPs likely to vote against and around 100 of her own 315 Conservative MPs voicing doubts she is expected to fail.
No one knows what would follow a defeat, and much would depend on its scale and style.
Political predictions haven't always been reliable over the past few years, so there remains a slim possibility that the Brexit deal could be passed – either in its current form or with an amendment related to the contentious "backstop".
Although around 100 Conservative MPs have suggested they will vote against, few want to risk a softer or canceled Brexit – more viable after Monday's European Court of Justice decision that Britain can unilaterally withdraw from the process – and none are keen on a general election. May could yet win over some waverers.
A victory would keep May in a job and keep Britain on track to leave the EU on March 29, 2019 in an orderly fashion. Further votes to enact the legislation would be necessary, however, so the parliamentary battle would not be over.
A victory would also put her government's confidence and supply agreement with the Democratic Unionists in danger, given the Northern Irish party's opposition to the deal.
2. Lose via amendment
Six amendments to the main government motion on May's Brexit deal will be voted on before the main event – and if they are passed, the central Brexit vote may not take place.
The most likely to be successful, if selected by House of Commons speaker John Bercow, is thought to be an amendment that rejects the prime minister's deal and also rules the possibility of a "no deal."
If it were passed, there would be no direct vote on May's deal: a big blow for the prime minister but not a knockout defeat.
It would probably allow her to carry on in the short term, but also limit her negotiating position if she were to attempt to get concessions from the EU. If she were to negotiate changes, another vote in parliament could take place next week.
3. Lose by a little
Managing expectations is an important part of politics, and speculation about a huge loss – 100 votes plus – could help May continue if she suffers only a narrow reverse.
The prime minister would probably try to get concessions from the EU and then hold another vote in the event of a defeat of fewer than 50 votes, buoyed by the possibility small changes could push the deal over the line.
She could also change tack, and argue for the "Norway" option – keeping Britain in the single market and allowing free movement to continue – that probably has a majority in parliament. This would be a big U-turn, however, and could probably only be pursued under a new leader.
But a loss of any margin would have serious consequences. The opposition could call a vote of no confidence in the government, though it may wait to see if May's own Conservative MPs make a renewed attempt to topple her.
4. Lose by a lot
A defeat of 100 MPs or more would be tough for May to survive.
Given that around 100 of her 315 MPs are in the government and bound to support the deal, a triple-figure loss in parliament would mean half of the Conservative Party voting against their own prime minister.
May has bounced back repeatedly over the past two years, but such a loss would almost definitely result in a leadership challenge if there was not a vote of no confidence in the government first.
A completely new deal based on the "Norway" option, a "no deal", an election, a government of national unity or a second referendum would all be on the table.
5. No vote
Weekend reports that May could postpone the vote and try to get concessions from the EU before putting a new deal to parliament were denied by Downing Street, but governments don't tend to hold votes they're likely to lose.
With all the indicators suggesting May is heading towards a defeat, a surprise move to delay the vote isn't out of the question.