As the clock ticks, though, British businesses are growing nervous. So far this year, investment in the auto sector has been about $840 million, according to the Society of Motor Manufacturers and Traders, an industry group. If that trend continues, the annual total will be well below the $3.2 billion invested in 2015, the last full year before the vote on European Union membership. Carmakers worry that leaving the European customs union would mean the imposition of tariffs and the disruption of complex international supply chains, both of which would raise their production costs.

At the same time, many banks are planning to relocate members of staff, in the expectation that firms based in London will lose the right to offer services across the European Union once Britain leaves the single market. And airlines will be affected unless a deal is reached to protect their right to fly to and from continental Europe. The budget airline easyJet has already announced plans to set up a new carrier, with headquarters in Austria, to allow it to continue operating flights across the bloc after Britain’s withdrawal.

Trying to steady the ship, Justice Secretary David Lidington dismissed reports of political infighting as little more than the product of summer garden parties: “too much sun, and too much warm prosecco.”

Few are buying that, however, and many analysts say they expect the feuding to continue until Mrs. May is pushed aside and a successor is named. But solving the leadership crisis may take time, which Britain can ill afford as far as the withdrawal process is concerned. And as Mrs. May herself has signaled, forcing her out could lead to a new general election that could be won by Labour and its leader, Jeremy Corbyn. So the jockeying, backbiting and carping might continue for some time.

Either way, the feuding reflects more than internecine battles among the Conservative grandees. It also reflects a growing, if belated, realization that there are few good options for Britain.

A so-called cliff-edge withdrawal that cuts many ties with the European Union without establishing new trade arrangements could lead to a sharp recession and an unpopular jolt to voters who had been promised a sunny future in a prosperous trading nation.

At the opposite end of the spectrum is what is being called the Norway option, in which Britain would leave the European Union but try to remain a part of its economic structures. That would put the country in a worse position than it is in today, forcing it to pay money to the bloc and to accept European rules without having a say in making them.