Mvume Dandala is a respected advocate for African social justice
Opposition South African presidential candidate Mvume Dandala has told the BBC he would reopen a corruption case involving his main rival if elected.
African National Congress leader Jacob Zuma was accused of corruption in connection with an arms deal.
He denied the charges and the case against him was recently withdrawn.
Bishop Dandala said all implicated, including people from his Congress of the People party, would have to face the consequences of their actions.
His party, Cope, was founded last year after former President Thabo Mbeki was ousted following a power struggle with Mr Zuma.
The Independent Electoral Commission (IEC) reports that more than 23 million people, including 16,000 of the South African diaspora, have registered to vote in what is being seen as the most keenly contested election since the end of apartheid in 1994.
Voting has already started for those who are disabled, pregnant and those who will be temporarily out of the country on Wednesday.
Election officials and security force members who will be on duty on election day also go to the polls on Monday and Tuesday.
Bishop Dandala told the BBC's Network Africa programme that if Cope won the general election, the party would aim to tackle corruption within the first 100 days of office.
Asked if he would reinstate the charges against Mr Zuma, he replied: "We will certainly reopen the investigation of the arms deal.
"Whoever gets fingered - even if those people are serving in the Congress of the People - they will have to face the law and have their names cleared or take the consequences of their actions."
He said he did not wish to "personalise" the issue of corruption, but said it was an issue that was not being dealt with "head on".
"It is a fact that in this country there are many people
who have been suspended from their jobs, but have been kept on their salary - some for as long as 18 months," he said.
"What this country needs are leaders who are going to have the strength of will to actually stand up and say: 'Let's deal with this lest this cancer spreads all over our body politic and our life as a nation.'"
Mr Zuma has repeatedly denied allegations of graft, racketeering and money-laundering over a multi-billion dollar 1999 arms deal.
The National Prosecution Authority (NPA) threw out the case earlier this month, saying there had been political interference.
The latest opinion polls suggest that Cope could get as much as 15% of the national vote.