Throughout South Africa's election campaign there has been speculation as to whether Thabo Mbeki, leading a new ANC government, will have the stature and vision to replace the iconic Nelson Mandela.

But Mr Mbeki will also have to deal with a political challenge from another quarter - from Mr Mandela's former wife.

Winnie Madikizela-Mandela remains one of the most important and controversial figures in South Africa. She is the ANC's most high-profile advocate of the poor. She travels tirelessly through the most impoverished areas and forcefully demands change.

"Some of us made the mistake of thinking that we are free," she told cheering voters on the campaign trail in the Cape flats. "But we are not free as long as our people remain as poor as they are. The revolution we should all be engaged in today is the liberation of our people from poverty."

The "mother of the nation"

Ms Mandela has spent years courting the devotion of these poor, black voters. And despite findings by the Truth and Reconciliation Commission linking her with killings, and despite her divorce from President Mandela, she still brings huge support to the ANC.

"She's powerful. She's very strong. She stands for what she says," one supporter in a crowd told BBC News. "We have already forgiven her." But has the ANC?

Ms Mandela has proved she is a force to be reckoned with. After the 2 June elections, in which she is certain to win a seat, the party must decide if it believes Winnie Mandela can once again be a political asset.

Rise and fall of Winnie Mandela

The ANC cannot discount Winnie's popularity with the poor

It is clear that Winnie Mandela has been a huge embarrassment to the party.

The woman known as the "mother of the nation" last year was found guilty by South Africa's Truth and Reconciliation Commission to have authorised or sanctioned murders and to have allowed her home to be used as a place for assault and mutilation.

She was also convicted over the murder of 14-year-old activist Stompei Seipei Moketsi who was kidnapped by her guards and later found dead. Initially, she was sentenced to six years in jail. She appealed and had the sentence reduced to a fine.

It was a bittersweet victory. At 64, Ms Mandela was virtually disowned by the party she had helped to build.

Staging a comeback?

In this election, Winnie Mandela has worked hard to keep her supporters, as well as a very low profile.

"Winnie Mandela is a very good self-publicist. She knows a photo opportunity," says David Coetzee of Southscan, a southern African newsletter based in London. "But throughout the campaign she has chosen not to make any deeply controversial or high-profile campaign statements.

"I think she anticipates that she will be brought back into the fold in a real way within the ANC after her period of semi-exclusion. She is hoping Thabo Mbeki will find a way."

But according to Howard Barrell, a former ANC member and current political editor for the South African Mail and Guardian, the ANC is not likely to welcome Ms Mandela with open arms.

"Thabo Mbeki is too smart to have Winnie Mandela in any position of real power in his government," he told BBC News. "He recognises that the opposition and elements of the business community would point incessantly to the presence of Winnie Mandela when expressing any dissatisfaction about the level of investment in the country."

Mr Coetzee added: "The government needs to decide if in times of continuing economic trouble, it's better to have a populist politician in government. I don't think she will be given a cabinet post but he knows he needs her to keep the constituency on his side."