Editorial: Will Boris Johnson become the third Conservative prime minister to be undone by Brexit?

Thanks to a vote by 138,809 dues-paying members of the Conservative Party, the United Kingdom is about to experience a dramatic and, for many, disorienting change in its political leadership. The dour and disciplined Prime Minister Theresa May will hand over the keys of 10 Downing Street to the flamboyant Boris Johnson, who defeated Jeremy Hunt, his successor as foreign secretary, in by-mail balloting. As a journalist and politician, Johnson is infamous for outrageous and offensive statements. (Think of a more erudite Donald Trump.)

But differences of personal style are less important than the fact that Johnson campaigned on a promise that he could accomplish what May failed to achieve: an expeditious withdrawal of the U.K. from the European Union that would serve Britain’s interests.

In remarks Tuesday after his victory, an ebullient Johnson said: “We’re going to get Brexit done on Oct. 31, we’re going to take advantage of all the opportunities that it will bring in a new spirit of can-do, and we’re once again going to believe in ourselves. Like some slumbering giant, we’re going to rise and ping off the guy-ropes of doubt and negativity.”

But the new prime minister embarks on his new duties with a handicap of his own making: his insistence that the U.K. will leave the EU on Oct. 31 with or without a deal with Brussels.

There is a reason why the implementation of Brexit has proved to be such a political bramble bush. When voters approved withdrawal in a referendum in 2016, severing trade and political ties with Europe seemed to many Britons a simple proposition. It has proved to be anything but that.

Untangling decades of financial and legal connections between the U.K. and the rest of Europe is a complicated proposition, which is why May acted responsibly under the circumstances in negotiating a gradual divorce with Brussels that would safeguard Britain’s economic interests. (The governor of the Bank of England has warned that a no-deal departure from the EU poses “material risks” of economic disruption.)

The terms May reached with the EU also addressed a political problem that was barely discussed before the referendum: the fact that taking the U.K. out of the EU might mean the return of a ”hard border” between Northern Ireland, which is part of the U.K., and the Republic of Ireland, which will remain in the EU. A seamless border has shored up the Protestant-Catholic peace process in Northern Ireland.

To preserve that state of affairs, British and European negotiators agreed to a so-called “backstop” provision under which the U.K. would essentially remain in the EU’s customs union and Northern Ireland would retain even closer links to the EU. The backstop would go into effect only if no new trade deal were reached between Britain and the EU.

The backstop has been controversial and played a role in the repeated refusal of Parliament to endorse the deal May negotiated. In one of those votes, Johnson reluctantly supported the withdrawal deal May negotiated, but now he seeks a new deal without the “monstrosity” of the backstop.

It’s doubtful that the EU will agree to such a stripped-down agreement, increasing the possibility of a no-deal Brexit. Yet there is little appetite in Parliament for a departure from the EU without a deal. Last week the House of Commons voted to prevent the prime minister from suspending Parliament in the run-up to the Oct. 31 deadline.

Ideally British voters would be given an opportunity to reconsider their endorsement of Brexit in a second referendum. Jeremy Corbyn, leader of the opposition Labor Party, has sent maddeningly mixed signals about Brexit. Corbyn said recently, however, that he supports a referendum on any withdrawal deal with the EU negotiated by a Conservative government. In such a vote, he said, Labor would support remaining in the EU “against either no deal or a Tory deal that does not protect the economy and jobs.” Johnson said last year that a second referendum “would provoke instant, deep and ineradicable feelings of betrayal.”

If Johnson adheres to his position that Oct. 31 is the “do or die” deadline and no agreement with the EU is reached by that date, he could face a no-confidence vote in Parliament and a general election.

Since he seems highly unlikely to allow a new referendum, the new prime minister should do the next best thing and apply his “can-do” philosophy to the task of securing a deal that would make the best of the Brexit blunder. If he doesn’t recognize the need for compromise — including on the Northern Ireland issue — he could become the third Conservative prime minister to be undone by Brexit, following David Cameron, who resigned after the 2016 vote, and May. Only this time the Conservative Party also could find itself out of power.