Labour has been reduced to such a pitiful state for two main reasons. A structural transformation is making it difficult to sustain the electoral coalition that has propelled left-of-center movements to victory in the past. And the response to this structural shift that Corbyn pursued has proved to be toxic.

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Back when Labour was capable of commanding convincing electoral majorities, it held together a broad class coalition. It was the natural party of working people, with overwhelming support among the less affluent and less well educated. At the same time, it enjoyed strong support among large sections of the middle class, attracting many university students, schoolteachers, and civil servants.

Although these two sides of the bourgeois-proletarian coalition have always differed in their cultural attitudes, they had significant economic commonalities. Both had an interest in high wages and strong unions. And both relied on the welfare state for the schooling of their children, for access to good doctors, and for the knowledge that they would be able to retire in dignity.

So long as the main focus of electoral politics was on economic questions, the leaders of the Labour Party could therefore hold this broad coalition together. Many Labour policies, such as generous spending on the welfare state, appealed to both.

But in the past decades, partisan alignment has shifted away from matters of economic policy toward what one might call questions of culture, such as immigration and, of course, Brexit. And whereas middle-class voters in large urban areas have progressive attitudes on immigration and strongly oppose Brexit, working-class voters tend to be highly critical of immigration and favor leaving the EU. Most of the working-class constituencies that have now swung to the Conservative Party resoundingly backed Leave in the 2016 referendum.

So Labour is now being pulled in two opposite directions. Many of its middle-class voters feel that the party is not sufficiently liberal on cultural issues; as a result, they are tempted to opt for more consistently progressive alternatives such as the Green Party. Meanwhile, many of its erstwhile working-class voters feel that the party’s leaders have come to look down on their cultural views; as a result, they are tempted to vote for the Tories, or even for more extreme alternatives such as the Brexit Party.

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The rise of culture as the main cleavage of Western politics helps explain the slow death of social-democratic parties in many countries across the West. In Germany and France, and from Italy to Sweden, left-of-center parties have failed to find a political message that can reassemble the old bourgeois-proletarian coalition.