Boris Johnson's historic victory on Thursday was his own. He purged the party of die-hard Remain heel-diggers, set the agenda of "get Brexit done," and won, tearing the heartland out of the Labour coalition and earning the largest Tory majority since 1987.

But Labour leader Jeremy Corbyn's loss was also his own. Labour's 202 seats in the newly elected parliament will mark the weakest representation for the party since 1935. Labour hemorrhaged support, shedding over 2.5 million voters and 7.8 percentage points of the popular vote — and those voters fled in all directions, some staying home, some going to the Tories, and some going to the Liberal Democrats, who though they lost seats increased their share of the popular vote by over 4 percentage points.

Corbyn has already said that he will not lead his party into the next election, but the future of Corbynism remains up in the air. And American Democrats are already debating the question of whether Corbyn's debacle holds lessons — and warnings — for them.

Center-left pundit Jonathan Chait fired an early shot, collecting a variety of left-leaning writers who lionized Corbyn, made analogies to the campaign of Sen. Bernie Sanders, and called on Democrats to embrace a sharp shift to the left. The U.K. election was "a test of a widely articulated political theory ... that Corbyn's populist left-wing platform is both necessary and sufficient in order to defeat the rising nationalist right," Chait said. "Corbyn's crushing defeat is a decisive refutation." Left-wing Sanders voters and their ilk should now abandon this theory, he concluded, and embrace the need for moderation.

But American left-wingers glommed on to Corbyn for a reason: Though he fell short of victory, he led a surprisingly successful election campaign in 2017. Corbyn won 262 seats in that election, a gain of 30, and fully 40 percent of the popular vote. That's nearly the percentage that Tony Blair won in his 2001 victory. And he didn't win it by running as Tony Blair; he won it by running as Jeremy Corbyn. Moreover, Americans already tried defeating a right-wing populist-nationalist by running an establishment center-left candidate. Why should we blithely assume Joe Biden would do better than Hillary Clinton?

So are there any lessons to be learned from Corbyn's collapse? I believe there are — but they aren't as simple as tacking to the left or the center.

What changed from 2017 to 2019? One difference is that in 2017 Corbyn was a fresh face generating new enthusiasm from a previously moribund base. Party membership had swelled and there was a sense of momentum and change. But the larger difference was the context of his contest. Theresa May was an uninspiring leader who carried the baggage of a deeply unpopular Tory austerity program, and who was trying to split the baby on Brexit in a way that was unpopular with everyone. That gave Corbyn an opening. In a way, his surprising strength in 2017 was more akin to Trump's strength in 2016 — the fringe insurgent animating new voters and scaring the establishment — and Theresa May more like Hillary Clinton, trying to appease the backbench Brexiteers as Clinton tried to appease the Sanders wing of the Democratic Party, but failing to excite enthusiasm thereby.

In 2019, by contrast, Johnson was running on a clear program of getting Brexit done and ending the gridlock of a hung parliament. But he was also running against the austerity of the Cameron/May years. Corbyn, meanwhile, couldn't take a clear position on Brexit because of divisions in his camp on the subject, which opened up space for the Liberal Democrats to be the party of Remain and the vehicle for anxiety about Corbyn's extremism.

The Tories moved to the right on the key national question at issue — Brexit — and to the center on economic matters. But they didn't run as Nigel Farage-style "little England" reactionaries, but as "one nation" conservatives. They co-opted a populist issue, but folded it into a much more centrist overall stance. That put them in a significantly more popular place than where they were before. And what did Corbyn's Labour do in response? They moved to the left across the board, not just on core questions of economics and social welfare. Their stance on immigration, for example, was extremely left-wing, effectively abolishing the distinction between citizen and resident and embracing freedom of movement even with non-EU nations. This move was driven not so much by Corbyn but by the views of party activists, who took the party leftward on a host of other issues as well. Even discounting Corbyn's problems with antisemitism, or his past support for the I.R.A., the platform his party ran on cannot be fairly described as a "one nation" campaign document.

The consequence wasn't just a historic loss, but a catastrophic reduction of the Labour coalition in geographic terms, which makes it much harder to convert votes to seats. And this reduction was already evident in 2017. In that election, Corbyn won 262 seats with 40 percent of the popular vote. In 2001, Tony Blair won only slightly more votes — 40.7 percent — but won a huge majority of 413 seats. In 2005, Blair won 355 seats with 35.2 percent of the vote, and in 2010 Gordon Brown won 258 seats with 29 percent of the vote. This week, Corbyn was only able to squeeze 202 seats out of his 32.2 percent vote share.

There are multiple factors at play in that change — the rise of Scottish nationalism, for example, and the shifting positioning of the Liberal Democrats — but a quick glance at the electoral map reveals the result: Labour is reduced to a few islands of red in a sea of blue. That's a map that should look all too disturbingly familiar to American Democrats.

And the lesson to Democrats should be similarly plain. Though the right sometimes can, the left cannot win on the basis of divide and conquer. They cannot move to the left on every issue simultaneously, and they cannot run a campaign that actively alienates voters who live outside the major metropolitan areas. To win a hearing on any issues where they do want to move left, they have to earn the trust that they will stand for, and listen to, the entire nation, not just the portion of it that is culturally congenial.

That doesn't rule out moving to the left — even sharply — on specific issues. A left-wing candidate could also be a cultural uniter. A cultural conservative like Ross Douthat can express a higher degree of comfort with Sanders than might be expected, even though Sanders is very liberal on cultural issues, simply because Sanders shows little personal enthusiasm for dividing the country along culture war lines. But Sanders himself has been pulled even further leftward by his party's activist wing on a host of issues — including immigration — that inspire distrust among more culturally conservative but economically receptive voters, much as Corbyn was. If that remains the pattern, Democrats should worry that history might repeat itself.

Donald Trump is not going to run as Boris Johnson. He’s going to run a relentlessly divisive, base-animating campaign, just as he as governed. That gives the Democrats an opening — if they will take it. The lesson of the U.K. election is that neither left-wing populism nor centrist technocracy is sufficient to defeat right-wing populism. What is needed is a "one-nation" liberalism that aims to heal rather than excite our cultural divisions, a liberal nationalism that stands for the country that actually exists, but as a nation, and promises to move it forward together.

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