He’s the anti-austerity candidate who had to borrow support to get nominated for the Labour leadership race. Now he seems to be leading it.
So who is Jeremy Corbyn? Here’s what you need to know:
Jeremy Bernard Corbyn
:: Real world experience
In terms of jobs, not so much, but has been a committed campaigner and a politician who passionately champions the causes he supports: CND, free Nelson Mandela, justice for Pinochet victims, Guildford Four, Stop The War and now anti-austerity.
He became a Labour councillor in Haringey at 25 and then MP for Islington North in 1983 at age 33.
:: Family history
Son of an engineer and maths teacher, born in Chippenham, Wiltshire. Brother Piers is a weather forecaster and climate change denier. Married three times and has three sons, with second wife Claudia Bracchitta.
:: Education – state or private?
State and comprehensive state at that. He is vehemently opposed to selection. So much so, he split with Ms Bracchitta in 1997 because he did not want his son, Ben, to go to a grammar school but to the then failing Islington comprehensive school.
A little ironic as Mr Corbyn received a grammar school education (Adams Grammar in Shropshire).
Ms Bracchitta won the education battle and Ben went to Queen Elizabeth boys’ school in Barnet but the couple split because of it.
:: Political chops
Labour Party rebel and thorn in the side of New Labour. He has defied the Labour whip nearly 300 times since 2005.
Firmly anti-Blair, he helped to organise the Stop the War coalition to campaign against the war in Iraq.
Has courted controversy. In 1984 he invited IRA representatives, including Gerry Adams, to the House of Commons 14 days after the Brighton bombing.
He is popular with his constituents and won 60% of the vote in Islington North in May with a majority of 21,194.
Oh, and he is a five-time winner of the Parliamentary Beard of the Year.
:: Centre-Left, Centre-Right?
Left-Left. His politics have been likened by some on the right of Labour to the populist Left-wing Syriza in Greece.
Mr Corbyn is not about tinkering around the centre ground. He is firmly of the view Labour lost the election because Ed Miliband did not go Left enough.
Policies include scrapping tuition fees – paid for by increasing tax on company profits, cutting subsidies for businesses, stronger anti-tax avoidance rules, richest paying greatest proportion of tax.
The anti-austerity Left-wing candidate who has become the surprise frontrunner of the leadership race. He borrowed support and became leadership candidate by the skin of his teeth because the party wanted a “broader” field.
Has said he has no expectation of leading the party but he has put on impressive displays of unflappability in interviews and has acquitted himself well at hustings.
He has secured the backing of the powerful unions and should not be underestimated – something the party is beginning to realise.
Mr Corbyn is successfully mining the powerful seam of sentiment that runs “if you are not Left enough you are not Labour”. There’s a nasty Twitter war playing out on this one.
His election could usher in a second leadership contest in a couple of years’ time, the floor cleared for the likes of Chuka Umunna, Dan Jarvis and Kier Starmer.
Most likely to say: “Wealth creation is a collective process between workers, public investment and services, and, yes, often innovative and creative individuals.”
Least likely to say: “I agree with George Osborne.”
:: Team Corbyn:
Diane Abbott, Frank Field, John McDonnell, Dennis Skinner and David Cameron.
Actually the Conservatives are backing Mr Corbyn and have launched a Twitter campaign to encourage fellow Tories to pay £3 to become a Labour supporter so they can vote for him.
This led Tony Blair to name Mr Corbyn the “Tory preference” candidate – although being insulted by Mr Blair could actually end up helping him.