On Thursday, the United Kingdom—in its third general election in the past five years—gave a large majority to Prime Minister Boris Johnson’s Conservative Party, all but assuring that the United Kingdom will leave the European Union in a matter of months. Johnson, who replaced Theresa May as the leader of the Conservative Party this past summer, was forced to call a vote because his narrow parliamentary majority was not sufficient for him to pass the Brexit deal he negotiated with Europe. The results will likely lead to a renewed independence push by pro-European Scottish nationalists. They have already caused a shakeup in the Labour Party, which has been led for the past four years by the leftist Jeremy Corbyn and had its worst election results in decades. On Friday, Corbyn said that he hoped to lead the Party during a period of “reflection” but would not do so in any future election. Corbyn, who ran on a platform of left-wing economic policies, such as nationalizing utilities and raising taxes on corporations, is distrusted by many voters, in part because of his reluctance to take a clear position on Brexit and recent incidents of anti-Semitism within the Labour Party.

To analyze the results, I spoke by phone with David Runciman, a professor of politics at Cambridge University, a frequent contributor to the London Review of Books and the host of its “Talking Politics” podcast, and the author of the book “How Democracy Ends.” During our conversation, which has been edited for length and clarity, we discussed the roots of Boris Johnson’s remarkable political success, the future of Labour, and the election’s lessons for center-left parties around the world.

You wrote in an essay last month, “Because Corbyn has proved so intransigent while remaining so incompetent, all the cards keep falling Johnson’s way.” Is Corbyn’s leadership failure the main reason you think this election went the way it did?

Yep. I think there were two things going on here. It was clearly a Brexit election and clearly a Corbyn election. The Labour Party is going to gain some votes in some parts of the country. It is going to do O.K. in London, it is going to do O.K. in some university towns where Corbynism is popular. But Corbyn and Corbynism are catastrophes in a lot of traditional Labour seats that voted Leave. People will argue for a long time about whether Corbyn or Brexit takes a bigger share of the blame, but they go together, and the Corbyn project is done.

Corbyn is both a strong leftist and someone who basically hedged or triangulated on the single biggest issue of the campaign: Brexit. Do you view his political failure as being more about one of these things than the other?

I think that the hedge was a problem in the sense that something beats nothing in politics, and one party had a very clear position on Brexit, and one party had a much less clear position. But, more than that, I think the Labour position, for a lot of voters, meant more of the same, including another deal and another referendum. I think a lot of voters intuitively felt that that meant more confusion. When Theresa May last time tried to claim that she stood for something and Corbyn stood for confusion, people didn’t really buy it. People who were tempted to vote Labour thought the confusion was equally shared. This time, his position on Brexit just reinforced the idea that, if you wanted to know what would happen next, you had to vote Conservative.

And then there is also the fact that, since Brexit happened, Corbyn and the Labour Party have made a series of missteps. A lot of people are already saying that Theresa May’s deal could have passed if Labour M.P.s had backed it. That would have kept Theresa May in her post, and British politics would look very different. Corbyn never gave a lead on that. Corbyn was hedging it all the way along. There have been moments where the Conservative Party could have been boxed in, and now Johnson and the Conservative Party have broken through, and Corbyn carries a lot of responsibility for that.

Is there a specific thing you think he should have done?

There will be people who will say that he should have resisted the election. Who knows? I think, in hindsight, what we are going to see is that there were opportunities, and yet there is a feeling that, when we look at seats that voted Conservative, these are seats that voted Leave, and it was always going to be challenging for any Labour Party to know how to deal with those seats. But it is hard to imagine anyone doing it worse than Corbyn has done. All the evidence from people canvassing was that, in these seats, Corbyn’s name was being mentioned a lot, and a lot of traditional Labour voters had turned on him.

What is the profile of these voters?

Essentially, they are working-class voters. This is not unique to this country, and it is not unique to the election. [The economist] Thomas Piketty has made this point repeatedly, which is that the workers aren’t voting for the parties of the center-left—our party is called the Labour Party, but it is no longer the party of labor. It is the party of university graduates, of big cities, and of young people, and the other crucial thing that will emerge when people break down the vote in this election is that there is here, as there was in the Brexit vote and the Trump election, a big, big generational divide. Younger voters will still vote Labour, but we are learning with every one of these elections that younger voters will consistently be outvoted by people over the age of forty-five, and older voters in this election have gone overwhelmingly to the Conservatives, including older working-class voters.

Corbyn became more pro-Remain as the campaign went on. Should he have not done so and triangulated even more? Or do you view this election as essentially the same realignment based on education levels that we have seen over the past several years well beyond the United Kingdom, with not much to be done?

Education and age are the new divides, and you need to be a very skillful politician to triangulate. He doesn’t have those skills. I don’t think there is an extra level of triangulation he could have pulled off, because he is not a convincing triangulator, and that is another part of the problem here. He never really actually became more Remain. What he did was accept that his party was going to have to commit to a second referendum. The problem was that he didn’t say how he would go in that vote. I think people continued to suspect that, in his heart of hearts, he was fine with Brexit happening, but that then makes him seem even weaker.

What’s interesting about this election is that Corbyn is the same guy who ran against Theresa May, and people were gobsmacked on Election Night about how well he had done, picking up these seats that no one thought he could. And now here we are. He is still the same guy. He hasn’t changed much, and certainly the anti-Semitism charge has stuck much more, and it does seem that the Tories have hit home more on national-security questions. That seems to have made a difference. But he hasn’t changed in thirty years. What has changed is what the electorate thinks this election is about. And Johnson did have a stronger pitch than May did, not least that Johnson had a deal. And that deal will now pass. We are going to leave the European Union in six weeks. It is going to happen.