THE most influential business idea of recent years is Clayton Christensen’s theory of disruptive innovation. It is celebrated because it explains why so many tech companies come from nowhere to revolutionise their industries. But it also provides a good analysis of Jeremy Corbyn’s success in taking the Labour Party to the edge of power.

Mr Christensen, who teaches at the Harvard Business School, argues that the most interesting businesses start life on the margins. They succeed by spotting underserved markets and inventing ways of reaching them. Disruptive innovators start off by producing unpolished products for the bottom of the market. Successful incumbents dismiss them as cranks. But as they improve their products they end up revolutionising their markets and humbling yesterday’s incumbents. Think of classified ads (Craigslist), long-distance calls (Skype), record stores (iTunes), taxis (Uber) and newspapers (Twitter).

Jeremy Corbyn, Labour’s leader, spent 30 years on the margins of British political life, from entering Parliament as the MP for Islington North in 1983 to winning the leadership of the Labour Party in 2015. He was treated as at best a harmless eccentric who liked making his own jam and at worst a terrorist-sympathiser who threatened the Labour brand. But he spotted the biggest underserved market in British politics—the young—and provided it with what it wanted: the promise of a new kind of politics.

Youngish people, particularly 18- to 30-year-olds but also those in their 30s, have been abysmally treated by the British establishment. They have borne the brunt of the introduction of a pay-as-you-go welfare state, taking out big student loans while even rich old people get free bus passes and winter-fuel allowances. They have also been the victims of house-price inflation. Whereas older people have seen their homes rise in value, the young have struggled to get on the property ladder.

The 68-year-old Mr Corbyn turned himself into the champion of the young in part by resorting to the ancient art of buying votes, with a promise to get rid of university tuition fees. But he offered hope and enthusiasm as well as money. He reintroduced phrases that had been banned during the long, technocratic years of New Labour, such as “social justice”. He talked about promoting universal peace rather than nuclear deterrents. He even looked different from traditional politicians. Tony Blair forced his troops to dress in suits to impress middle England. Mr Corbyn sports a beard and looks unhappy in a tie.

Labour’s leader produced a new business model to cater for underserved audiences. Under the old one, politics was primarily done by professionals—the MPs—who chose their leader and went to the public every few years. Mr Corbyn advanced a participatory model in which MPs played second fiddle to Labour Party members and their vanguard of activists in groups such as Momentum. He will use his newfound power to push this revolution further: at the Labour Party conference in September, for example, he will try to reduce the percentage of MPs and MEPs required to nominate a candidate for leader from 15% to 5%.

Under the old business model the Labour Party did everything it could to avoid the “tax and spend” label. Mr Corbyn argued that the country was sick of austerity and inequality. His manifesto promised to nationalise industries, empower trade unions and boost public spending. Under the old model the left ran scared of the media. Mr Corbyn decided that the tabloids were not so much Rottweilers as paper tigers edited by old people who failed to realise that twenty- and thirtysomethings didn’t relate to stories about the IRA and the three-day-week.

New business models were combined with clever use of new technologies. Labour used a track by Lily Allen, a sympathetic popstar, to accompany a heart-warming video about how wonderful Britain might be if only it weren’t run by the wrong sort of people. But much of the social-media energy came from activists. Two young women created a program on Tinder, a dating app, to encourage potential dates to vote Labour. Corbynistas created websites such as The Canary, Evolve Politics and Skwawkbox. Facebook shares amplified the cacophony. The story of this election was not a Conservative collapse but a Labour surge, with Mrs May winning 42.4% of the vote and Labour 40%, an increase of ten points since 2015. Lord Ashcroft’s survey of 14,000 people on election day found that two-thirds of those aged 18-24 voted Labour, as did more than half of those aged 25-34. The first group to break substantially for the Tories was people aged over 55.

From outsider to incumbent

Mr Corbyn is now enjoying the revenge of all disruptive innovators. Moderate Labour MPs such as Chuka Umunna, who had been convinced that Mr Corbyn would go down to a catastrophic election defeat, are now lobbying for jobs in his cabinet. One reason why Theresa May called an election was that she was convinced that nobody would vote for such an extremist. Now one of the few things keeping the Tory party from tearing itself apart is fear that Mr Corbyn will win the next election.

The essence of disruptive innovation is that it is uncertain. For every Google there are several Netscapes. Winner though he may seem, Mr Corbyn is still 64 seats short of a parliamentary majority. His hard-left supporters could overplay their hand, particularly by driving Blairite “saboteurs” out of the party. Many people voted for Mr Corbyn on the assumption that he wouldn’t win: they wanted to give the Tories a bloody nose, not Mr Corbyn the keys to 10 Downing Street. Mainstream Labour MPs will turn on him at the first sign that his policies are not delivering. But for the time being the momentum is with him. R.A. Butler, a former Tory grandee, once describe politics as the “art of the possible”. Whether or not he ends up in Downing Street, Mr Corbyn has undoubtedly redefined the boundaries of the possible.

Economist.com/blogs/bagehot