Madikizela-Mandela was nominated from the floor during the second day of the ANC's 50th natioanl conference by a North-West delegate, Yvonne Makume, after failing to receive pre-conference nominations from any of the nine provinces.
However, when an independent electoral official called for the nomination to be seconded only a small group of delegates gingerly raised their hands.
While independent electoral officials asked delegates to raise their hands higher to be included in the count for the requisite 25 percent support for the nomination to succeed, Madikizela-Mandela began to consult her fellow National Executive Committee members on the podium.
In a departure from procedure Madikizela-Mandela walked up to the microphone and asked for a delay in the nomination procedure. "I want to consult with the structures so that I do not appear devisive," she said.
This was refused by ANC president-elect Thabo Mbeki, saying that nominations from the conference floor were by individuals and not party structures.
Madikizela-Mandela replied: "Comrade Thabo I think I do understand what is happening. (To) those comrades who nominated my name I apologise for having to decline". She did not elaborate.
Her decision was greeted by loud cheers and a standing ovation from the audience.
An official from the Electoral Institute of SA, who was conducting the elections then asked twice if there were any further nominations, and when there were not she announced: "I therefore am delighted to announce that comrade Jacob Zuma is the deputy president."
Although officials publicly denied there had been a count, they privately acknowledged that a figure of 125 - far short of the nomination threshhold - had in fact been tallied.
Sources close to the voting process said Madikizela-Mandela had then been offered the opportunity to save face graciously, by declining her "nomination".
Earlier a source close to Madikizela-Mandela insisted she would accept nomination. "Trust me she will stand," Sapa was told.
She had apparently been asked on Tuesday to decline a nomination from the floor by a National Executive Committee delegation, but had refused.
Describing himself as Madikizela-Mandela's best friend, Deputy Environmental Minister Peter Mokaba told journalists, she had decided long agocy.
Her decision "demonstrates the extent to which she loves her movement (the ANC)," he said.
He had accompanied a smiling Madikizela-Mandela out of the Great Hall at the University of the North-West on Wednesday arm in arm with Mokaba, after the nomination process.
She refused to answer questions from the hoards of journalists who swamped her, but paused to hug several supporters, before being whisked away in a white Mercedes Benz.
Mokaba said there had been no pressure on Madikizela-Mandela at all to withdraw from the race, saying the fact that she would not stand had been know to the ANC leadership for a long time.
Her decision had been taken before she appeared before the Truth and Reconciliation Commission - in which she was linked to at least 18 human rights violations.
Madikizela-Mandela was still a leader in the ANC, he said.
"One thing we (the ANC) will always be sure about is that she will always be with us. She won't go the route of (Bantu) Holomisa (who co-founded the United Democratic l always be with us.
She had withdrawn from the race because she did not want any devisions within the ANC, Mokaba said.
Cheryl Carolus, who on Wednesday relinquished her position as the ANC's acting secretary-general, later told a media briefing Madikizela-Mandela's decision not to stand was made at the same time as the seconders' votes were being counted.
"I don't want to speculate why Mrs Madikizela-Mandela chose that point to step down," she said.
The number of votes cast for Madikizela-Mandela were not presented to the conference because she stood down, Carolus said.
This figure "might be relevant for people who want to speculate on these matters - for us the important factor is that she withdrew," Carolus said.
She said conference delegates "remained very respectful" of Madikizela-Mandela. Carolus also denied suggestions that a vote to decide on the deputy presidency would have divided the party.
"The ANC has never been afraid of the democratic process," Carolus said.