On Sunday afternoon, Dominic Raab, Britain’s Brexit Secretary, went to Brussels to meet Michel Barnier, the European Union’s chief negotiator. The mid-afternoon meeting was announced only that day, and it seemed to suggest that a deal was almost done. Last Friday evening, in Luxembourg, E.U. ambassadors were briefed that the talks were going well. Over the weekend, the German newspaper Süddeutsche Zeitung quoted from an internal E.U. document saying, “Deal made, nothing made public (in theory),” pending a possible announcement by the British government on Monday. There have been rumors in London for several weeks that Theresa May, the Prime Minister, was willing to agree to new compromises in the talks—a dense, technical array of backstops, protocols, and procedures—in order to be able to announce a deal with the E.U. at a special Brexit summit next month.

But Sunday’s meeting was a bust. At 6:43 P.M., Barnier tweeted, “Despite intense efforts, some key issues are still open, including the backstop for IE/NI to avoid a hard border”—a reference to the problem of a frontier on the island of Ireland, an issue that has bedevilled the negotiations for more than a year. A couple of hours later, Britain’s Department for Exiting the European Union issued its own mournful update: “There remain a number of unresolved issues relating to the backstop.” Neither Raab nor Barnier said what happened in the meeting, but the Guardian reported that the chief obstacle remains May’s ability to sell her compromises back home. E.U. ambassadors were told that the “Brits need more time,” according to Sabine Weyand, Barnier’s deputy, the newspaper reported. “The problem is at the British end,” a diplomat said.

There is now a hole where the Brexit deal should be. A meeting of E.U. “sherpas”—high-level diplomats and interlocutors for the bloc’s leaders—which was scheduled in Brussels, on Monday, to start preparing the ground for the agreement, was cancelled. On Wednesday evening, the E.U.’s leaders will gather for dinner in Brussels; May was expected to address them with the outline of a deal. As of this moment, she has nothing but an anxiety nightmare.

The great sticking point—around the Irish border—has always been there. Since the Brexit negotiations began, in the summer of 2017, they have been vexed by the logical need to create a border between Ireland (a member of the E.U.) and Northern Ireland (part of the United Kingdom), and the political need not to have a border, in order to protect the island’s peace process. Squaring this circle would be hard enough under any circumstances, but, to pass legislation, May’s government relies on the ten members of Parliament who belong to the hard-line, pro-union Democratic Unionist Party. Any solution to “the Irish backstop,” as it is known, is likely to involve Northern Ireland staying more or less within the E.U.’s structures, while the rest of the U.K. takes a step away. This is a no-go for the D.U.P.

Nevertheless, the negotiators have been quietly trying to hammer out a deal along these lines. Last week, Arlene Foster, the leader of the D.U.P., had her own audience with Barnier in Brussels; the Party promptly threatened to bring down May’s government if such an agreement went ahead. On Sunday, e-mails sent by Foster were leaked to the Observer, saying that “the D.U.P were ready for a no-deal scenario,” indicating that May had lost the Party’s support.

At the same time, May’s Conservative Party is a barely coherent entity. Over the weekend, with the Prime Minister seemingly within touching distance of agreeing to the terms of the nation’s withdrawal from the E.U., her former Brexit negotiator, David Davis, called on May’s Cabinet to rise up against her, citing the compromises she has been willing to accept. “It is time for the cabinet to exert their collective authority,” Davis wrote, in the Sunday Times. “The authority of our constitution is on the line.” Boris Johnson, the former Foreign Secretary, who resigned this summer over May’s Brexit plan, described the potential Ireland deal as “a choice between the break-up of this country, or the subjugation of this country, between separation or submission.” At a “Leave Means Leave” rally in Torquay, Jacob Rees-Mogg, the jingoist Brexiteer M.P., told a crowd, “Dare I say, we have stood up to the French once or twice before,” before comparing the E.U. to the Mafia.

No one knows how many Conservative M.P.s will vote against whatever May is finally able to agree on with the E.U., but it’s clear that she will need at least some support from outside her party. According to analysts at Edelman, the communications company, May would need the votes of fourteen Labour M.P.s to have her Brexit deal approved by Parliament—a number that rises to twenty-four if she loses the support of the D.U.P.

On Monday afternoon, May stood up in the House of Commons and said that the broad shape of a Brexit deal was in place. “This is the time for cool, calm heads to prevail,” she said. Since becoming Prime Minister, in the summer of 2016, and taking responsibility for steering Britain out of the E.U., May has walked a narrowing path, between the marauding factions of her party and what is achievable in Brussels; between respecting a populist vote and national self-harm; between her country’s self-image and its relative decline. Now there is no path.