LONDON (Reuters) - Uncorking the spirit of British socialism was the masterstroke that handed Jeremy Corbyn the Labour Party's top job but he now faces a much bigger challenge -- convincing voters that an admirer of Karl Marx should be Britain's next prime minister.
Virtually unknown just months ago, the 66-year-old won the crown of Britain's second largest political party with 59.5 percent of the votes cast in an internal party vote.
A vegetarian who initially did not expect to win the contest, Corbyn has struck a chord with many Labour supporters by repudiating the pro-business consensus of former Labour leader Tony Blair and offered wealth taxes, nuclear disarmament and ambiguity about EU membership.
The victory gives Corbyn a mandate to take the 115-year old party back to its socialist roots and throw out the political rulebook that says British elections can only be won with the support of the center ground.
"We challenge the narrative that only the individual matters, and the collective is irrelevant," Corbyn said at his last campaign rally on Thursday, drawing cheers from a crowd crammed into every corner of a former church in north London.
"Instead we say the common good is the aspiration of all of us," said the anti-war campaigner, who is an admirer of "Communist Manifesto" author Karl Marx and Hugo Chavez, the late Venezuelan leader who delighted in berating the United States.
Often dressed in the style of a university lecturer -- complete with several pens visible in his shirt pocket -- Corbyn has promised to renationalize privately-owned industries, print money to fund large-scale infrastructure investment, and raise taxes on businesses and the rich.
He rarely uses the first person 'I' - a trait that advisers say reflects his desire to lead Labour without what he calls "top-down control-freakery" - code for the tight control exercised when Tony Blair was Labour leader from 1994-2007.
"Things can and they will change," Corbyn, said in a victory speech which began with criticism of the British media and ended with a vow to achieve justice for the poor and downtrodden.
He swiftly left the Labour event to attend a meeting in support of refugees on London's Trafalgar Square.
Corbyn has tapped an appetite for change, drawing back veterans of the party's 1980s hard-left heyday and giving some disillusioned young voters born during or after the 1979-1990 Conservate premiership of Margaret Thatcher their first taste of a mainstream socialist cocktail.
"His opposition to austerity is the thing for me. He's the only one to openly say that what's going on with this Conservative government is an ideological decision, and it's not something that has to happen," said Sam Peach, a 22-year old first-time Labour voter at a Corbyn rally in Edinburgh.
The surprise success of Corbyn's campaign, funded, he says, by his personal credit card until donations began flowing in, has drawn dire warnings that Labour will be annihilated at 2020 elections by a public that in May re-elected Cameron on a pledge to cut spending.
"The party is walking eyes shut, arms outstretched over the cliff’s edge to the jagged rocks below," warned Blair in one of three increasingly desperate pleas to voters to stop the Corbyn surge before the result was announced.
But, pleas from senior centrist Labour figures to elect 'ABC' (Anyone But Corbyn) backfired.
"Actually what has happened is that the grass roots of the campaign have simply become more resilient and more enthused by every attack," said Neil Findlay, a Labour member of the Scottish parliament who organized the Corbyn campaign in Scotland. "It has been utterly counterproductive."
Corbyn's campaign eclipsed those of his three rivals - Andy Burnham, Yvette Cooper and Liz Kendall - drawing sell-out crowds on a 99-stop tour of Britain that capitalized on dissatisfaction at Britain's political and economic status quo.
One Labour lawmaker, who did not want to be named, said he backed Burnham, but that he had been unable to persuade the rest of his family to do the same. They all voted for Corbyn.
Perhaps unsurprisingly for someone who travels around London by bicycle and buses, supporters often use words like 'normal' when describing his appeal.
"I wasn't interested in the Labour leadership contest at all until I saw him and listened to what he had to say," said Joe Reynolds, a carpenter living in London, and one of many queueing without tickets in the hope of getting into a Corbyn rally.
"The man seems genuine. He wants to stand up to big business and the corporations and look after the general mass of people."
First-elected in 1983 to represent a North London constituency, Corbyn's political career has reached a high that few, including the man himself, saw coming.
In June, Corbyn was persuaded by a small contingent of hard-left lawmakers to run in the leadership contest sparked when Ed Miliband's resigned after a heavy election defeat.
They felt their political views and those of the party's grassroots were under-represented by the other three candidates.
"He said 'alright, alright, alright, I'll have a go'," Corbyn's campaign manager John McDonnell told supporters at a rally, recounting the meeting where Corbyn eventually agreed to stand after other contenders had ruled themselves out.
The leadership bid was almost scuppered before it had truly started. Faced with a midday June 15 deadline, Corbyn's team were scrambling to find the 35 lawmakers they needed to get his name on the ballot paper.
McDonnell said there were just 10 seconds to go when the last nominations came through.
Corbyn says the there were actually two minutes to spare - the kind of earnest response that has spawned a parody account on Twitter dedicated to mocking his apparent lack of humor.
Such was the low probability initially given to a Corbyn victory, many nominations came from lawmakers who were backing other candidates but lent Corbyn their support in the interest of widening the debate over the party's future.
"I can't say I regret it," Neil Coyle, the 33rd lawmaker to nominate Corbyn, told Reuters. "It would have been a disservice to prevent him."
Coyle voted for Cooper. But the scramble for nominations highlighted concerns about whether Corbyn could bring the leftists together with the rest of the party to form an effective opposition to Cameron, he said.
"How is it that he's been in parliament since 1983, and yet he can't find 35 MPs (lawmakers) to put him on the ballot paper who genuinely think he'll do a good job?"
Whether he can hold his own party together let alone launch a serious challenge to win power will be the immediate issue. Within minutes of his election, a number of lawmakers said they would no longer serve in the party's senior team.
"I'll always be a critical friend of Jeremy's because I'm not entirely won over that the 'left' message is sufficient to win government in this country," said David Lammy, a Labour lawmaker.
"The big question is whether a broader offer to the left is enough to win in England," he said.
Conservative finance minister George Osborne, likely to be Corbyn's main opponent at the 2020 election, shares the view that his victory is a backward step for Labour.
"For most of my childhood and early adult life, a succession of Labour Party leaders reformed the constitution of the Labour Party. Neil Kinnock did, John Smith did, Tony Blair did, to make sure that it was more rooted in what the British people wanted," Osborne told the weekly magazine the New Statesman.
"If they want to go back to the 1980s, let them. The Conservative Party is not doing that."
Editing by Guy Faulconbridge and Angus MacSwan