Winnie Madikizela-Mandela has emerged as the top candidate in the vote for the national executive committee (NEC) of South Africa's governing party.
Ms Madikizela-Mandela's success follows Mr Zuma's election as leader
African National Congress (ANC) members voted in the 80-member NEC after sacked Deputy President Jacob Zuma defeated President Thabo Mbeki as party leader.
Some of Mr Mbeki's closest allies failed to make it onto the NEC.
In his first public comments since his defeat, Mr Mbeki said he did not plan to step down early as president.
"I would expect the government to serve its term until the elections in 2009," Mr Mbeki said at a news conference at government headquarters in Pretoria.
Tony Yengeni, former chief whip, convicted of corruption
Nozizwe Madlala-Routledge, sacked deputy health minister
Health Minister Manto Tshabalala-Msimang (known as Dr Beetroot)
OUT - Mbeki loyalists:
Deputy President Phumzile Mlambo-Ngcuka
Defence Minister Mosiuoa Lekota
Mr Mbeki said that he planned to work with his rival, whom he said had given "a summary of the way forward, to which all members of the ANC need to respond positively".
But Mr Zuma faces corruption charges, which prosecutors say are imminent. He has said he is ready to go to court to clear his name.
Referring to the allegations, Mr Mbeki said: "All of us in the ANC have insisted, even... Zuma himself, that the law must take its course."
Mr Zuma's supporters have always said the charges are a political conspiracy against him.
Ms Madikizela-Mandela, the ex-wife of former President Nelson Mandela, was endorsed by 2,845 of the 3,605 delegates to the conference in the northern town of Polokwane.
She has not been active in the ANC since 2003, when she was convicted of fraud.
Earlier this month she stepped back into the spotlight when she proposed a face-saving compromise deal between Mr Mbeki and Mr Zuma - a suggestion that was not taken up.
A prominent activist against apartheid during her then husband's imprisonment, Ms Madikizela-Mandela was convicted of kidnapping in 1991, in connection with the disappearance of a teenage activist who was subsequently found murdered.
The election of the NEC on Thursday follows the election earlier this week of Mr Zuma and five of his allies to the party's most senior positions.
Among the prominent Mbeki allies who did not make it onto the NEC were national Deputy President Phumzile Mlambo-Ngcuka, Minister in the Presidency Essop Pahad and his brother, Deputy Foreign Affairs Minister Aziz Pahad.
Ms Mlambo-Ngcuka was appointed by Mr Mbeki after he fired Mr Zuma in response to corruption charges in 2005.
Her husband, former chief prosecutor Bulelani Ngcuka, is seen by Zuma supporters as part of a conspiracy to bring down Mr Zuma.
Other Mbeki allies were more successful, with Housing Minister Lindiwe Sisulu in seventh place in the NEC race, and controversial Health Minister Manto Tshabalala-Msimang at number 55 - several places behind her recently-sacked deputy, Nozizwe Madlala-Routledge.
On Thursday, chief prosecutor Mokotedi Mpshe told South Africa's 702 Talk Radio that the investigation into Mr Zuma was complete, and that "all we are doing now is tying [up] the loose ends".
Mr Zuma refused to comment, only saying: "We'll cross that bridge when we come to it."
The charges relate to a controversial arms deal, which saw Mr Zuma's adviser Schabir Shaik jailed for 15 years.
Tony Yengeni, former ANC chief whip, who was convicted of fraud over the same arms deal, retained his place on the NEC.
He was released from prison in January just four months into a five-year sentence. His strict parole conditions were relaxed to allow him to attend the conference.