Finally, nearly three years after the referendum, the Brexit virus has contaminated its own opposition.

The people who have been fighting the project to get Britain out of the European Union are suddenly behaving exactly like their Brexiteering adversaries. This past week, debating proposals for how to finish the long process of Brexit, the “remainers” acted in the uncompromising winner-takes-all fashion of the “leavers.” British politics has changed from “the art of the possible” to a battle of true believers.

The Brexiteers’ desired outcome has not been accepted by liberals and internationalists, of course. But they seem to be increasingly infected by the methodology of Brexit — by its manner. Some kind of zombie contagion seems to have broken out in Westminster, passing from person to person until the characters you’ve trusted all along turn around, with blood-red eyes, and start trying to bite your head off.

Time itself seems to be slowing down so that weeks now feel like months. Brexit is like a black hole, sucking in energy, light and matter. There are no other news stories. There are no other considerations. There is nothing but Brexit, and it is driving everyone mad.

The sign that the opposition is gripped by the same maniacal fervor as the Brexiteers came on a night of high political drama. These evenings used to arrive once every few years and pass into legend. They now happen about once a day. On Monday, members of Parliament (MPs) took control of the process of leaving the E.U. from the government. It was the latest battle in a bout of constitutional trench warfare between Parliament and the executive, the likes of which we haven’t seen since the English Civil War broke out in 1642. The House of Commons voted to temporarily cancel something called Standing Order 14 — a rule that gives Downing Street control over the legislative timetable — and then started sitting on its own terms to debate whatever it liked. It was like a drab British version of the Tennis Court Oath at the start of the French Revolution.

Having seized the agenda, MPs used the time to hold a series of nonbinding indicative votes on what Brexit policy should be. There were four options to choose among: membership in the European customs union, which controls taxes on goods crossing borders; membership in the European single market, which harmonizes regulations across the continent; a second referendum to ratify whatever deal would be passed with the European Union; and a push for the government to simply revoke Article 50, the legal mechanism for leaving the E.U., and call the whole thing off.

The results were a disaster. Everything failed, but most of them only narrowly — by between three and 21 votes in a chamber with 650 members. (The measure to undo Brexit altogether lost by 101 votes, probaby because the word “revoke” is still completely toxic to those who are terrified of being seen as undermining the much-mythologized “will of the people” as expressed in the 2016 referendum.)

Some of the plans were put forth by MPs who accepted Brexit but wanted to limit the damage it would do to the British economy. Others were sponsored by those who wanted to stop it altogether. Critics of Brexit have been split between these two approaches — damage control and outright reversal — since the referendum passed. Together, the two groups have the numbers to put forward an alternative plan with majority backing. In each case Monday, they would have succeeded if they had joined forces. In each case, they refused to do so.

After the votes were read out, Nick Boles, the Conservative MP who authored the single-market plan, stood and addressed his fellow lawmakers. “I accept I have failed,” he said. “I have failed chiefly because my party refuses to compromise. I regret therefore to announce that I can no longer sit for this party.” And with that, he walked away. A voice called out after him: “Oh, Nick. Nick, don’t go, come on.” But he did not turn around. He literally crossed the aisle and went to sit alone, a newly independent MP.

Boles was one of the architects of a project to modernize the Conservative Party, whose moderate figures in 2005 attempted to cleanse it of its more jingoistic and hard-line policies. His departure was proof that the initiative was dead. It had been massacred in Brexit’s nativist spasm, in which nationalist zealotry trumped any other form of right-wing political discourse. But the symbolism went even further than that: Boles was accepting that the very concept of pragmatism was impossible in his party.

This is the Tories, the single most successful and long-lasting political party in the Western world. It is sunk in a mire of crazed puritanism. Anyone who refuses to go along now either leaves of their own accord or is forced out.

On vote after vote Monday, the Tory leaders simply boycotted the process and abstained. They scorned every compromise, every articulation of a middle ground. It wasn’t because the party supports Prime Minister Theresa May. They won’t vote for her deal in sufficient numbers to get it through, either, which is why it’s failed each of the three times she’s brought it to the floor.

But what’s terrifying about the closing days before the latest deadline for Britain to crash out of the E.U. with no deal, this coming Friday, is that such puritanism is no longer restricted to the government benches. It is now present among the opponents of Brexit, too. Labour MPs who support the People’s Vote campaign for a second referendum refused to back proposals for a softer Brexit on Monday, as did the moderate Liberal Democrats party. Even the Independent Group, a newly formed collection of former Conservative and Labour MPs who say they’re willing to work across traditional tribal loyalties, refused to support them.

The same applied to many proponents of a softer Brexit. All they had to do was offer support to the People’s Vote campaign as a ratification process on their plans, and they could have secured much wider backing for their proposals. But they would not. Everyone called for everyone else to compromise, while never seeming willing to do so themselves. So instead, it turned into a circular firing squad. All the options lay dead on the floor.

Why is this happening? How is a country that was once famed for its moderation, stability and practical judgment turning into a political abattoir?

The answer is identity politics. Brexit is a right-wing culture war conducted in populist terms. It is not really about the E.U. It is about people’s sense of who they are. It is about wanting a world of walls, separating people and ideas and political structures from one another. But it is not just a desired outcome: By now, it is also a way of doing things. The Brexit mind-set does not compromise or accept caveats. It is politics in primary colors. There is victory or national slavery, and nothing in between.

It leaves the country in an extremely perilous situation. The government’s latest wheeze, expressed in a statement from May on Tuesday night, is to extend Article 50 again and try to bring opposition leader Jeremy Corbyn on board to see if they can find a deal that works for both Labour and the Conservatives. By the end of the week, no signs had emerged that they would be able to discover one. And May’s request Friday to delay the April 12 deadline until late June was met with skepticism by E.U. leaders.

Even this attempt, which shows an openness the prime minister has not exhibited before, faces the same problems: If the plan does not include a People’s Vote, Corbyn loses a chunk of his supporters, inside and outside Parliament. If it includes a soft Brexit, those People’s Vote types won’t support it, and May loses most of her own party in the bargain. Whichever way you look at it, political puritanism makes the mathematics of a Brexit majority hard to imagine.

The country is stuck, frozen in indecision. Parliament is reenacting the end of “Reservoir Dogs.” And still the clock ticks mercilessly down. Puritanism has provided no answers whatsoever except pain and failure. Unless MPs quickly rediscover Britain’s tradition of pragmatism, things are about to get very ugly indeed.

This article has been updated since it was first published on April 3.

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