Deputy president Cyril Ramaphosa won endorsement from most African National Congress branches to succeed president Jacob Zuma as ruling party leader, giving him an edge - but not a guarantee of victory - in this month's election.
The victor of the party race will be well placed to become the country's new president in 2019.
Zuma was found not guilty of raping Fezekile Kuzwayo in 2006, before he became president in 2009.
During a radio interview with 702's Karima Brown, Ramaphosa was asked what his views were on the rape allegation that Khwezi Khuzwayo brought against Zuma in 2005.
Pushed on whether he believed Kuzwayo's allegations, he said: "I know how hard and painful it is for a woman to garner the courage to stand up and say "Yes I was raped".
He did however also say he understood how hard it is for women to come forward with allegations of sexual violence, and he had sympathy for Khwezi.
President Zuma and Deputy President Ramaphosa talking at the OR Tambo centenary in Kantolo.
The rape allegation has haunted Zuma for years despite his acquittal in court and has remained a popular topic in South Africa as the.MeToo movement spreads.
Ms Kuzwayo was HIV-positive and Mr Zuma's statement during the trial, that he showered after unprotected sex with the woman to guard against possible infection, provoked ridicule.
He was head of the country's national AIDS council at the time, and the case fuelled public outrage over AIDS prevention and sexual violence in South Africa.
"It must be one of the most hard decisions that she has to make", he said.