UK Prime Minister Theresa May spent months negotiating a deal with the European Union on the terms of Brexit, Britain’s exit from the EU.

On Tuesday, the UK Parliament voted to reject the deal by a resounding 432-202 margin — the largest legislative defeat any prime minister has suffered in modern British history.

May’s defeat should dispel any illusion that there is a happy ending to the Brexit story. The truth of the matter is that the project that defined May’s premiership — negotiating a Brexit deal acceptable to both the EU and pro-Brexit legislators in her Conservative Party — was structurally impossible. The terms on which Conservative Brexiteers wanted to leave the EU were not acceptable to EU negotiators, and the compromises necessary to bring EU negotiators on board were not acceptable to Conservative Brexiteers. No amount of negotiating could address this dilemma.

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May’s tenure in office — which appears likely to continue for some time, despite the Brexit deal’s devastating defeat — was premised on the lie that she could work out a Brexit deal palatable to all sides.

Now, in the clarifying light of this vote’s failure, it’s time to be honest. Barring a dramatic and unexpected change, there are two plausible outcomes to the Brexit drama. Either the UK exits the EU without a deal by the March 29 deadline, which virtually every expert agrees would result in economic catastrophe, or else the country pulls back from the brink and decides to remain in the EU.

These options aren’t what the Brexiteers promise, but it’s difficult to envision any other ones after the failure of May’s deal. To quote another famous Conservative prime minister: There is no alternative.

Theresa May was asked to turn a campaign of lies into political reality

Theresa May was not prime minister when the initial referendum on leaving the UK was held back in June 2016. Her predecessor, Conservative PM David Cameron, had supported staying in the EU. His gamble was that UK voters would vote to stay and the pressure to leave from Conservative hardliners and the far-right United Kingdom Independence Party (UKIP) would dissipate.

That’s obviously not what happened. The Leave campaign won principally by manipulating British xenophobia, but also by making a series of grandiose promises: Britain wouldn’t be hurt economically by quitting the EU’s common market; in fact, it would stand to regain hundreds of millions of dollars a week to spend on its health care system. Britain would have no problem getting out of shared EU regulations; Brexit would “take back control” of the legal system.

Some of those promises, like the health care spending numbers, were exposed as lies the day after the Brexit vote. But the British people had just voted to leave the EU to usher in utopia, and Theresa May was brought in to make that a reality.

To do so, she would need to thread a needle: somehow minimize the hit to the British economy by keeping as much access to EU markets as possible while simultaneously removing the UK from as many EU rules and regulations as possible to fulfill the “take back control” promise.

The problem was that there was a direct trade-off between these two goals. The EU negotiators didn’t want to allow Britain unfettered access to EU markets while it made its own rules on everything from immigration to product standards; that would be giving them a better deal than EU members. So there needed to be some kind of compromise.

The deal that Parliament voted on Tuesday was full of such compromises. It punted on a lot of central issues, including immigration, but allowed the UK to leave while keeping enough EU rules in place to avoid immediate catastrophe.

But even this was too much for the pro-Brexit Conservatives, who believed May was selling out to the Eurocrats. Their most heated objections focused on the so-called “Irish backstop,” a complicated provision designed to keep the border between the Republic of Ireland (an EU member) and British-controlled Northern Ireland open indefinitely.

The Brexiteers believed the backstop would force the UK to adhere to a number of EU trade and migration regulations for years — and they had a point. The problem is that the backstop was nonnegotiable for Ireland and the broader EU, which refused to grant Britain the power to unilaterally screw up a very tense border arrangement in a part of the world that has been wracked by conflict as recently as 1998.

This is the specific issue, more than any other, that caused more than 100 Conservative legislators to betray their prime minister and vote with the left-wing Labour opposition to defeat May’s Brexit deal. But focusing too much on the Ireland situation would be a mistake. Remember, this deal didn’t even settle the UK’s final status on thorny issues such as migration from EU member states; it left that decision to future negotiators to decide. There were any number of different specific, technical issues on which May could not have satisfied the EU without betraying the Brexiteers, and vice versa.

The fundamental and insurmountable problem is that Brexit was premised on a fantasy — a painless withdrawal from the European Union — that no prime minister could have delivered. Theresa May is no one’s idea of a great negotiator, but her fundamental project — a negotiated settlement to the Brexit situation — was doomed for structural reasons beyond her control.

The honest choice: no deal or second referendum

The overwhelming defeat of May’s deal is clarifying.

The margin of defeat, the largest anyone can remember, means that no amount of tinkering at the edges with EU negotiators can fix the situation. Barring some kind of shocking development, the May deal is well and truly dead.

With this fantasy put to rest for the time being, it’s easier to see the plausible alternatives. One option is a no-deal Brexit, in which the trade and immigration rules governing Britain’s relationship with Europe simply cease to take place. The consequences of this could be pretty devastating; in the UK’s Prospect Magazine, deputy director of the British Influence think tank Jonathan Lis compiled 36 eye-popping ones:

Food will rot. We import about half of our food and feed, and 70 per cent of that comes from the EU. The bosses of Calais and Dover have warned of 30-mile tailbacks and possible infrastructural collapse. Experts have already warned that supermarkets will soon run out of supplies. (Hence the stockpiling.)

Also, Lis notes, commercial aviation would be crippled. “Aviation is currently governed by the Single European Sky, European Aviation Safety Agency and aviation single market,” he explains. “You fall out of those, and pilots and planes lose their certification overnight.”

If that doesn’t sound that bad, consider this: Bank of England projections suggest that the impact of a no-deal Brexit on the British economy could be worse than the damage it suffered during the 2008 Great Recession. A no-deal Brexit would represent a historic catastrophe: an unnecessary, and entirely self-inflicted, economic crisis.

If this seems awful, and a negotiated settlement appears politically impossible, then there’s a third option: Britain just stays in the European Union.

Some members of Parliament in the opposition Labour Party have been pushing a people’s vote, a referendum on the final terms of Brexit that effectively represents a do-over of the first vote. There’s a lot of grassroots support for this among the British left and political center; polling suggests that 54 percent of Britons would vote to remain this time around.

Another, less plausible option would be for May to simply announce that she was for staying in the European Union and ask Parliament to vote to end the Brexit process (the initial referendum was not legally binding).

Realistically, either no deal or a second referendum is the most likely alternative. Sure, Britain and the EU could agree to postpone the March 29 Brexit deadline, but it’s not clear what future negotiations could accomplish. It’s been two and a half years since the Brexit vote, and no one has come close to figuring out how to resolve the fundamental tension between what British Brexiteers demand and what the EU can live with. Their best attempt just went down in flames.

Curiously, UK politicians appear to be in denial about this.

May — assuming she stays in office — has given no indication that she has a plausible plan for overcoming parliamentary opposition to her deal. Corbyn’s Labour Party is vowing to work on “securing a Brexit deal that would work for you” if given the top job. Never mind that there is no Brexit deal that would “work” for Brexit proponents and the EU; Corbyn, who, unlike much of his party, appears to sympathize with the Brexit project, stolidly refuses to entertain the idea of a second referendum.

The entirety of Britain’s leadership class seems to be obsessed with securing something impossible. If any good comes of today’s vote, it’s that some Britons might wake up to the reality of the situation.