How might it all end? No one knows for sure, but here are four possibilities.

No Deal

Mrs. May has long insisted that no deal is better than a bad deal, though she has been saying that less emphatically since her election debacle. Business leaders say that a bad deal would have to be very punitive indeed to be worse than a breakdown of talks. That would lead to a “cliff edge” for British companies, which would lose their current arrangements for access to European markets in 2019.

While significantly less likely since the election, the “no deal” possibility should not be dismissed out of hand. The European Union requires progress on Britain’s “divorce terms” before the future trading relationship can be discussed. The divorce includes sensitive issues like Britain’s outstanding financial commitments to the bloc — which could result in a bill of as much as $75 billion. Mrs. May (or a successor if she falls) might reject such a hefty price tag, walk out of talks and try to rally support among voters in Britain by claiming that Europeans were trying to punish them for leaving. For a fragile government, that would be a high-risk strategy indeed — but so would agreeing to an expensive and economically damaging exit.

A Clean Break

Mrs. May says she wants Britain to leave the bloc’s Customs Union, which eliminates tariffs, so that Britain can make global trade deals independently. She also wants to quit the European single market, which smooths trade in services, because leaving would end the free movement of European workers, in that way restoring national control of immigration. According to her plan, those arrangements would be replaced by a comprehensive trade agreement with the European Union.

While this remains a likely outcome, with the Labour leader Jeremy Corbyn reportedly telling people that he expects to be prime minister within six months, there is obviously a long way to go. Mrs. May could lose a vote of confidence, leading to a disruptive Conservative leadership contest and the possibility of the Labour Party profiting from the division to win back control of the government. That could further dilute support for a clean break.