Today, the British parliament will finally decide whether to support or reject the EU-exit deal that Prime Minister Theresa May's government has painstakingly negotiated with the European Union.
If it feels like we've been here before – we have. Last month, May postponed this very vote after it became clear that her plan was headed for defeat.
Since then she has weathered a Tory Party no-confidence vote, but there's little to suggest that her deal – which is too moderate for hardline Brexit supporters while also being too far-reaching for Brexit opponents – has any better prospects this time around.
Roughly 100 members of her own Tory Party are rumored still to oppose it. But if the UK hurtles out of the EU on 29 March without a deal, the economic effects on both sides of the English Channel could be severe. The clock is ticking.
So if May's deal is crushed today, as it looks like it will be, what would come next? There are four main scenarios:
Extend and Renegotiate –May has begun preparing the groundwork to extend the Brexit timeline beyond March 29 and tweak the deal further. Would the EU agree to such a request? Growing political troubles in France and Germany have made the continent warier of allowing a "no-deal" Brexit, meaning that European leaders might soften their earlier resistance to reopening negotiations. But even if Brussels were to approve an extension, Mrs. May would still be stuck with a domestic quandary: with her Tory Party split over Brexit, she would face pressure to try and peel off votes from the opposition Labour Party in order to win approval at home for any new deal.
A Second Referendum –A defeat today would bolster calls for a second Brexit referendum. While May has ruled out such a vote, many within her Tory Party believe it's the only way to clarify what Britons really want from Brexit. This path has its fair share of landmines though: who, for example, gets to decide what specific question is presented to British voters in a second go-around? How would the result affect the current Brexit timeline? And after a majority of British voters (with large turnout) supported Brexit in 2016, would a do-over undermine trust in UK democracy?
Early elections –If May's deal is buried today, the Labour Party plans to immediately put forth a parliamentary vote of no confidence to topple her government. May probably has enough support to defeat it, but a successful no confidence motion would trigger new elections. That would upend negotiations with the EU entirely and could even lead to a Labour government that would likely favor closer economic ties with the common bloc than what Mrs. May has negotiated.
A "No-Deal" Brexit –If the UK and EU are unable to come to a solution before the March 29 deadline at all, and the EU is unwilling to offer the UK more time, Britain would then leave the EU without a comprehensive deal governing future economic relations. Both sides want to avoid this outcome, but the closer we get to 29 March, the more likely it looks.
The bottom line: The size of May's loss today will tell us whether she can sustain enough support to negotiate a new deal or if instead we're heading for a more tumultuous end to the Brexit drama.