The African National Congress (ANC) will finally begin voting this afternoon for its new leader in a chaotic election which the challenger Jacob Zuma is being tipped to win.

Thabo Mbeki, the South African President is vying with Mr Zuma, his controversial and resurgent former deputy, for the leadership in the first public contest the party has seen in 55 years.

The 4,075 delegates at the five-day conference were poised to begin voting after a lengthy delay which saw the two factions wrangling over procedures.

Mr Zuma’s supporters had objected to plans for electronic voting, arguing that the results could more easily be altered. The Mbeki camp opposed manual voting, fearing that delegates would be more likely to be intimidated.

A compromise was finally reached to elect the top six ANC positions manually and the remainder electronically, but the dispute only served to further deepen the bitter split between the two camps. “It has been the worst possible start the conference could have had,” an ANC insider said, amid raucous scenes previously unimaginable for a party so united during the long struggle against white minority rule.

Their rivalry has seen delegates to the party conference booing, singing partisan songs and challenging attempts by the old guard to keep the process dignified.

As the conference opened on Sunday, delegates loyal to Mr Zuma jeered leaders seen as allies of Mr Mbeki, waved pictures of the challenger in defiance of a ban, and called for the dismissal of Mosiuoa Lekota, the national chairman.

As the President finished an address to the conference on Sunday, Zuma supporters burst into the anti-apartheid song “Bring me my machine gun,” which has become the anthem of the former deputy president.

With the voting process so complex, a result is not now expected until tomorrow morning. There had been talk of a possible deal to postpone the decision on the leadership until next year, at which time Mr Mbeki would be allowed to bow out gracefully both as ANC leader and President.

But with Mr Zuma now commanding a comfortable majority among delegates and consequently losing appetite for such a bargain, this now seems increasingly unlikely.

If Mr Zuma, loved by the rank and file, takes the ANC top job a form of dual leadership will take effect, with Mr Mbeki in the presidency and his rival the head of the most powerful political organisation in the country.

Mr Zuma, who was dismissed as deputy president in 2005 after he was linked to a corruption scandal, will also become the most likely successor to Mr Mbeki once he steps down as President in 2009. However the humiliation of such a defeat might well force Mr Mbeki from office sooner, while a triumphant Mr Zuma could use his newfound power to force an early election.

The Zuma camp is unlikely to wait until 2009 to push home its advantage and many observers feel that a compromise will be done where the country goes to early national elections some time next year.

Mr Zuma, 65, has made an astonishing comeback since being fired by Mr Mbeki, despite simultaneously fighting rape and corruption charges. His corruption trial collapsed dramatically last September while earlier in the year he was cleared of raping a family friend, though he emerged with questions over his sexual responsibility and judgment.

During last month's nominating process, he secured 62 per cent of the vote and the backing of the influential youth and women’s leagues.

He is regarded as a left-winger who would push redistributive economic policies, in contrast to Mr Mbeki’s free market approach which many say has failed to lift the poorest South Africans out of poverty. The former head of the ANC’s militant wing, he is seen as earthier and more approachable to the sometimes aloof Mr Mbeki, a tactician who sprinkles his oratory with Shakespearean references.

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