Alberto Pezzali / AP

Minutes after last night’s exit poll indicated that Boris Johnson’s Conservatives would win an 86-seat majority, a friend turned to me and said: “The Tories just won the 2024 election.” This was not merely a defeat for Labour and its left-wing leader, Jeremy Corbyn—it was an annihilation. The party, which has been in opposition since 2010, now faces another decade out of government.

When Corbyn was elected Labour leader four years ago, he was often compared to Michael Foot, who led the party to a crushing defeat in 1983 against Margaret Thatcher. Back then, Foot’s left-wing manifesto was described as “the longest suicide note in history.” Corbyn’s manifesto was nearly three times as long, and even less successful: he has led Labour to its worst showing since 1935. “In the past hundred years no opposition has lost seats after 9 years in opposition. None,” observed the former Labour adviser Torsten Bell.

The tide has gone so far out for Labour that it is now predominantly a party of the English cities and their commuter suburbs. Seat after seat in its traditional strongholds across central and northern England and north Wales fell to the Conservatives. Before the sun was up, Corbyn had said he would not lead the party into another election.

The stage is now set for a vicious battle over Labour’s future, between Corbyn’s left-wing followers and the remnants of the previous, center-left iteration of the party. Socialists against social democrats. Did Corbyn merely fail this time—or has this result discredited Corbynism as an idea? Is it enough to remove the man, or must the party also reject his ideology?

Corbyn’s defenders are already out in force, blaming the defeat solely on Brexit—a once-in-a-generation issue the party could not tackle—rather than on the leader. “There is absolutely no appetite to go back to the centrist policies of old,” Laura Parker, the national coordinator of Momentum, a campaign group founded to support Corbyn’s leadership, said after the exit poll. “We will keep the Labour Party socialist.”

It is true that Brexit has exposed a bitter divide in British politics. We call it Remain versus Leave, but that is also shorthand for city versus town, young versus old, university graduate versus nongraduate, cosmopolitan versus protectionist. Johnson appears to have united the Leave vote behind his party, whereas the Remain side splintered. Voters could choose among Labour, the Liberal Democrats, and the Greens, plus Plaid Cymru in Wales and the Scottish National Party in Scotland, all of which backed a second referendum on leaving the European Union. (In Scotland, the nationalists won a landslide, increasing the chances of another referendum over its independence.)

But really, come on. Much like Labour’s grumbles about Britain’s print media being dominated by the right, its Brexit problem falls into the category of “Okay, but you should have a strategy to address that.” Less than two months ago, the Labour leadership directed its members of Parliament to support triggering a general election while Brexit still hung in the balance, with Britain scheduled to leave the EU on January 31. That meant Johnson was always going to run a campaign based on his exit deal—and the promise that he alone could “get Brexit done.”

Attributing the loss to Brexit neatly avoids the other obvious culprit for Labour’s catastrophe: its leader. Phil Wilson, the former MP for the northern-English constituency of Sedgefield, once held by Tony Blair, called blaming Brexit “mendacious nonsense.” He added: “Jeremy Corbyn’s leadership was a bigger problem. To say otherwise is delusional.” Ian Murray, the former Labour MP in Edinburgh, echoed that. “Every door I knocked on, and my team and I spoke to 11,000 people, mentioned Corbyn. Not Brexit but Corbyn.” Former Labour Home Secretary Alan Johnson said on live television, “Corbyn was a disaster on the doorstep; everyone knew that he couldn’t lead the working class out of a paper bag.”

Under this analysis, Corbyn is to blame for alienating Labour’s traditional working-class base, and appealing instead to metropolitan liberals. Corbyn himself is solidly middle-class and metropolitan—a teetotal vegetarian who grows marrows and represents a London constituency. His historically unpopular campaign carried strong overtones of piety, as if anyone who did not support it was morally defective. In the election campaign, he promised that schools would critically teach Britain’s colonial past, and his government would seek to atone for British imperialism. He also pledged to allow adults to self-identify their gender, and suggested that the law might legally recognize nonbinary people. Such policies are extremely popular among left-wing accounts on British political Twitter, but perhaps less interesting to swing voters in places such as Redcar, where the steelworks recently shut down under the Tory government, and where voters nevertheless switched from Labour to the Conservatives.

Within the left, though, it is Corbyn’s attitudes toward foreign policy that have caused the most bitter rows. Until he became Labour leader, he was largely uninterested in domestic issues; what really motivated him was anti-imperialism. He protested apartheid in South Africa. He took up the plight of the Chagos Islanders in the Indian Ocean, displaced by the British military. He was, famously, against the Iraq War, a foreign-policy and humanitarian disaster that stained Blair’s record. Corbyn liked to depict himself as a man of peace, advocating a “political solution” to the Syrian civil war (which has instead ended with al-Assad triumphant, backed by Russia and Iran). He met members of Sinn Fein, the political wing of the Irish Republican Army, when the latter was carrying out a bombing campaign against British rule of Northern Ireland. He told a rally in 2009 that he had invited “friends” from Hamas and Hezbollah to Parliament. (He later said he regretted the phrase.) These positions worried even senior members of his own cabinet; Corbyn’s health spokesman was caught out in a leaked recording telling a friend, “On the security stuff … I think the machine will pretty quickly move to safeguard security.” In other words, Britain’s civil service would be alert to the possibility that Prime Minister Corbyn would be a threat to national security.

Added to this, the Labour leader consistently showed, according to the most charitable interpretation, a blind spot about the modern forms that anti-Semitism can take. The party’s slow response to complaints about members posting anti-Semitic slurs and conspiracy theories, or provocations such as comparing Israel to the Nazis, compounded the issue. The lingering scandal dented Corbyn’s much-vaunted reputation as a “lifelong anti-racist.”

Any reckoning with Labour’s terrible performance in 2019 has to account for its relative success under Corbyn two years ago. What went right then and wrong now? Then, the party made solid gains and deprived Theresa May, Johnson’s predecessor, of a Parliamentary majority. Corbyn was a much newer leader, only two years into the job, and Conservative attacks on him for wanting to make Britain into a Marxist hellscape did not connect. (It helped that the Labour manifesto was relatively cautious.) The 2017 Conservative campaign also relied heavily on the assertion that Labour was blocking Brexit—yet the opposition had just voted alongside the government to start the formal two-year countdown to leaving the EU. The evidence was not there.

Fast-forward two years and Brexit has indeed been blocked, although as much by the ultra-Brexiteers in the Conservative Party as the Remainers in other parties. (About 30 Tory “Spartans” voted against May’s three attempts to get a deal through Parliament, saying it was not a clean enough break with the EU.) That nuance was lost in the campaign, though, with Johnson boasting endlessly about his “oven-ready deal.” Corbyn not only proposed a renegotiation and a second referendum but refused to say whether he would then campaign to leave or remain. His team saw it as clever triangulation, staying above the bitter divide. To many, it looked disingenuous or indecisive.

The “brilliant defeat” of 2017 had two other consequences. The first was that the left of the party, which had been warned by the center that it was sacrificing electability for moral purity, felt vindicated—and let everyone know it. Corbynism was a viable electoral strategy, it seemed. A handful of centrist MPs were sufficiently alienated that they left Labour, while others decided to keep their heads down, not criticize the leader, and hope for the best. This bitter loss now unleashes their anger. Holding together the left and center-left within one party will take an extremely skillful politician indeed.

The second consequence was that Corbyn did well enough to stay as leader. No obvious heir to his movement has emerged. The hard left was so marginalized during the Blair era that there is a missing generation of socialist MPs, and many of the most ardent Corbynites in Parliament are relatively inexperienced. That now offers the center-left a chance at a comeback.

Had Corbyn stepped down after the 2017 election, he might have been remembered as a principled left-winger who brought his party closer to government. By staying in place, and leading Labour to such a catastrophic loss, he will instead be condemned as the man who granted the Conservatives their second consecutive decade in power. Corbyn is defeated. The survival of Corbynism hangs in the balance.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.