With some 4,000 voting delegates expected to descend on the northern city of Polokwane over the weekend for the African National Congress (ANC) leadership conference, Mbeki denied he was intolerant of dissent and bemoaned the emphasis on personalities over policies in his contest against Jacob Zuma.

But while Mbeki received a warm endorsement from Deputy President Phumzile Mlambo-Ngcuka, Nobel prize-winner Desmond Tutu said neither candidate possessed the qualities needed to lead "a nation in distress".

Zuma, sacked by Mbeki as deputy head of state in 2005 when his financial advisor was jailed for fraud, is the clear frontrunner having won around 60 percent of provincial branch nominations.

Analysts say defeat for Mbeki would severely dent his authority in his last two years in power before he has to step down as head of state.

While he would not be drawn on his chances of victory, Mbeki said in a newspaper interview that his prospects were being undermined by negative perceptions about his style of leadership.

Jacob Zuma © AFP/File Gianluigi Guercia

"If, as an ordinary member, I was told this by someone credible, whose word I had no reason to doubt, I would vote against that person."

Asked whether people were afraid to confront him because they feared him, Mbeki replied: "I've heard this and I don't understand it. Do I look as if I've got horns?

"It's said that I block and inhibit open discussion -- that's puzzling to me; it's completely untrue."

Mlambo-Ngcuka said she expected the five-day gathering from Sunday "to be one of the most difficult conferences we've ever had".

But she said the results from the preliminary rounds of the contest should not necessarily lead to Mbeki's demise.

"I think President Mbeki is going to win. People mistake nomination for an election," she told public radio.

Zuma, who is still deputy ANC president, has been spending the final days of the campaign on his home turf in the eastern KwaZulu-Natal province, meeting Zulu King Goodwill Zwelithini on Thursday and seeking the blessing of local community leaders and churchmen.

Desmond Tutu © AFP/File Leon Neal

"We're very worried that this leader had relations with a woman who regarded him as a parent and, although he is very likeable, we have to ask ourselves: 'What is happening in the ANC?'"

Although Zuma was cleared of rape, his legal troubles are still not over as he faces the possibility of being charged with corruption after recently losing a bid to have a series of search warrants declared illegal.

Tutu, the former archbishop of Cape Town, also added his voice to accusations that Mbeki does not tolerate criticism.

"Criticism and debate have always been the lifeblood of democracy," he said.

Helen Zille, leader of the main opposition Democratic Alliance, said the contest had shown the ANC in its true light and the country as a whole had been the loser.

"The leadership contest has been characterised by bitter infighting, character assassination, and an almost total absence of debate on policy. Meanwhile, state delivery across the country has been held up," she said.