Tony Blair usually keeps out of party politics. But this time, the former British prime minister felt forced to intervene in the debate over the leadership of the Labour Party. "If your heart is with Corbyn, get a transplant," Blair warned his party colleagues about the ultra-leftist candidate.

Former Health Secretary Andy Burnham was considered the favorite for the party chairmanship. But surveys suggest outsider Jeremy Corbyn is leading the race to lead Labour - and that has the party in a frenzy. The party establishment says Corbyn would make Labour unelectable with his extremist agenda.

"If we make the wrong choice in this election, we will be condemning our world to a Tory future," Yvette Cooper, one of the three candidates competing with Corbyn for the party chairmanship, said. Veteran Labour lawmaker John Mann described the election campaign as a "farce" and even urged it be called off. Liz Kendall, who also is running for the party presidency and who is close to Blair, warned that Labour under Corbyn would turn into a British Syriza.

Footsteps to the left

But who is Jeremy Corbyn? The 66-year-old with the white beard has sat in the Commons for more than 30 years for the London borough of Islington. He has never held a higher office and was never a member of a shadow cabinet.

He is a backbencher, and a very difficult one. No Labour MP has defied the party whip and voted against the party line as often as Corbyn - more than 200 times between 2005 and 2010 alone.

Corbyn is a left-winger out of conviction. He demonstrated passionately against the war in Iraq and continues to demand that Blair be charged with war crimes. The vegetarian, teetotaler and car-hater wants to abolish tuition fees and nationalize the post office and railways. He is committed to combating nuclear armament, and he wants to leave NATO. He criticizes free trade with the US, and wants to tax the rich more.

In his long political career, he called for the abolition of apartheid in South Africa, while siding with socialists in Venezuela and Hamas in the Palestinian territories. He not only opposes capitalism, but also the monarchy. At the funeral of the Queen Mother in 2002 Corbyn wore a bright red jacket.

Wedded to dogma

His consistency sometimes produces strange fruit. He quarreled with his second wife about which school their son should go to. For Corbyn only a comprehensive school came into question, while his wife preferred a grammar school.

The couple divorced as a result of the dispute.

Grassroots support

While the party leadership wants to hinder Corbyn, his straightforwardness is attracting grassroots support. People queue up to hear him make a speech. He is also supported by the trade unions.

Unison, the largest trade union for public sector workers, is recommending its members choose Corbyn. "He talks our language, his language is the language of hope," Unison boss Dave Prentis said.

Corbyn "has opened a floodgate of dreams, making people feel good about themselves," writes "Guardian" columnist Polly Toynbee. "He is right about welfare, austerity, tax avoidance, renationalizing rail and mail, Trident, housing and myriad other touchstones. He's authentic to the tip of his beard."

Careful what you ask for

Labour's squabbles are good news for the Conservatives. According to polls, the Labour Party is currently doing worse than in the May elections. Some 76 percent think the party in its present state is unelectable.

The conservative "Daily Telegraph" writes with glee that a Corbyn victory would secure the Tories' hold on power for years. The paper is even going so far as to call on its readers to vote for the far-left outsider. That's because everyone who registers as a Labour supporter for only three pounds can vote in its leadership election. British media are already reporting on around 140,000 "new" members who have infiltrated the party.

On September 12, party members will decide whether Corbyn will lead them. Labour could be facing a hot autumn.