With around 95% of votes counted, Zuma’s African National Congress (ANC) had taken 66.1% of the vote.
Zuma has been outspoken in his criticism of Mugabe’s autocratic rule. He supports of the power-sharing agreement between Mugabe’s Zanu-PF and the Movement for Democratic Change, led by Morgan Tsvangirai but he has criticised his predecessor Thabo Mbeki’s "quiet diplomacy" towards Zimbabwe.
Tendai Biti, finance minister in the unity government and secretary-general of the MDC, is looking forward to a Zuma presidency. "I don’t think it will be quiet diplomacy," he said. "That was buried on 22 September 2008, the day Mbeki was removed. I expect a more forthright, honest and hands-on diplomacy.
"Jacob Zuma is not Thabo Mbeki and that means a lot. I know the man and meet him regularly and know the way he thinks."
Unlike Britain and the US, South Africa has thrown its weight behind the power-sharing agreement, despite concerns that Mugabe and his allies remain dominant. Biti added: "South Africa is leading the way in supporting us directly, including financial assistance. They recognise the problem requires international support They’ve been calling for that consistently."
Zuma, who has a track record on brokering peace deals in conflict areas, is thought to be keen to keep the ear of Mugabe. But he has family ties with the MDC: last year one of his daughters married the son of Welshman Ncube, a leading party figure.
David Coltart, Zimbabwe’s minister of education and an MDC senator, said: "The key for us is that Jacob Zuma wins. Of the last three – Thabo Mbeki, Kgalema Motlanthe and Zuma – he has been the most outspoken. I think Mugabe will be fairly nervous about his relationship with him."Zuma and Mugabe are very different characters. You would never see Mugabe singing a song in front of the faithful and dressed in casual attire."
South Africa has long been regarded as the democratic anchor of the continent. After the violent crackdown that followed last year’s disputed elections in Zimbabwe, Zuma said: "We cannot agree with Zanu-PF, we cannot agree with them on values. We fought for the right of people to vote. We fought for democracy."
The provisional result appears to show the ANC falling short of the two thirds of the vote needed to change the South African constitution.
The ANC’s closest rival was the Democratic Alliance with almost 16.4% of the vote. The Congress of the People, formed by politicians who broke from the ruling party, stood below 7.5%