WHEN Ken Livingstone served as leader of the Greater London Council in the 1980s—a prototype of the London mayoralty he held between 2000 and 2008—all but one of the current candidates to become leader of the Labour Party were still students. The result of their race will be announced on September 25th.

The day before, the outcome of another Labour contest will be declared. Mr Livingstone is running to be Labour's candidate in the capital yet again. If he wins, and goes on to replace the Conservative incumbent, Boris Johnson, in 2012, it will be his third stint in London's top political job.

His main rival is Oona King. Ms King was tipped for great things when she became an MP in Labour's 1997 landslide. But Parliament rarely seemed to suit her and, in 2005, she lost her east London seat to a fringe candidate who denounced her support for the Iraq war. At 42, she is closer to the average age of Londoners (36) than the former mayor (who is 65). As the product of a black American father and a Jewish mother, she suits what is one of the most diverse cities in the world. Next to her, Mr Livingstone, who has built a career on political iconoclasm, almost seems like a member of the establishment.

Yet Mr Livingstone has a gift for campaigning and a mastery of machine politics that his rival lacks. “Red Ken”, as he has long been known, has secured the nominations of major trades unions, such as Unite and the GMB. He also has the backing of most of the Labour members of the London Assembly. He is by some distance the favourite to win the candidacy.

Moreover, the main fight in 2012 should be an eminently winnable election for Labour—and thus, perhaps, Mr Livingstone. London remains difficult terrain for the Tories, who failed to pick up target seats such as Hammersmith at the general election. There are whispers that Mr Johnson may not run again. Even if he does, his party will be much less popular than it was in 2008, when he ousted Mr Livingstone. London will not be spared the cuts to public spending imposed by the Conservative-Liberal Democrat government.

Mr Johnson is also struggling to control the city's troublesome transport unions, who crippled the Tube system with a strike on September 6th and 7th. And while he has lots of small accomplishments to his name—a ban on alcohol on public transport, a popular, citywide bicycle-rental scheme—he cannot point to a defining triumph, such as the congestion charge that Mr Livingstone introduced in 2003.

Still, there are drawbacks to a Livingstone candidacy. At national level, Labour is striving to shrug off its past. Its youthful leadership candidates are trying to distance themselves from Tony Blair, Gordon Brown, Lord Mandelson and other titans of the New Labour era. A mayoral candidate who predates that epoch, and who has already been rejected at the polls, would make it hard to persuade voters that the party is truly changing. That is why many senior Labour figures, even left-leaning ones, hope that Ms King somehow beats the indestructible Mr Livingstone.