With around a third of the votes counted in South Africa's landmark general election, the ruling ANC looked set to win a fifth consecutive term in office Thursday, but with a significantly reduced margin.
A provisional count showed the ANC well ahead, with just under 60 percent of the popular vote, after millions of determined South Africans -- including hundreds of thousands of first-time "born free" voters -- turned out in their droves.
Twenty years after South Africans of all colours wowed the world by voting to end apartheid, they had shrugged off sporadic violence to vote in the first poll since the death of democratic hero Nelson Mandela.
His African National Congress had been widely expected to win, returning Zuma for a second term, but strong urban turnout appears to have proved a boon for the party's political foes.
The ANC's initial tally was down significantly from the 66 percent it won at the last election, amid successive scandals surrounding its leader President Jacob Zuma.
Anything less than 60 percent for the ANC would be seen as a major upset and prompt speculation about Zuma's role as leader.
Casting his ballot in his home village of Nkandla, Zuma predicted the "results will be very good" but conceded the campaign had been "very challenging".
Zuma has been a lightning rod for criticism of the ANC and has been pilloried for the government spending $23 million (17 million euros) of taxpayers' money to upgrade his private home.
The opposition Democratic Alliance was reported to have increased its share of vote to 27 percent, up 10 points versus the 2009 election, although the tallies could still change significantly.
DA leader Hellen Zille told AFP early Thursday she expects the final tally to be "about 23 percent."
"We'll see how it goes, of course we hope it will be more, we did as much as we could."
A record 25 million voters registered for the elections amid mounting anger over joblessness, inequality and corruption, with turnout currently said to be over 70 percent.
"People died for this right. They must not waste it," said Nobel peace laureate Desmond Tutu, a liberation struggle veteran who has said openly he will not vote for the ANC this time.
Pansy Tlakula, chairperson of the Independent Election Commission, said voting "proceeded without serious incident in almost all areas" with a "very high volume of voters" reported in metropolitan areas.
The ANC however reported a member of its campaign staff was killed "by an opposition party member" as he sat outside a polling station in KwaZulu-Natal province.
The eve of the ballot was also marred by isolated incidents of violence, with police and 1,850 troops deployed to several areas to keep order.
In Bekkersdal near Soweto, protesters had thrown rocks at police vehicles and set fire to a polling station just hours before it was due to open.
But residents vowed not to be dissuaded from voting. They poured into the township's 15 polling centres, many on foot and some pushed in wheelchairs and wheelbarrows.
Commentators have billed this election as the last to be dominated by the memory of apartheid.
Throughout the campaign the ANC relied heavily on past anti-apartheid glories and on the outpouring of grief over the death in December of its former leader Mandela to shore up support.
But the party's heroic past often collided with South Africa's harsh present.
Polls showed many voters disaffected with the country's current crop of leaders and willing to consider the centrist opposition Democratic Alliance or left-wing firebrand Julius Malema.
Malema's Economic Freedom Fighters party is less than a year old, but early results showed it winning around four percent of the vote. If sustained that could be enough for more than a dozen seats in parliament.
It has campaigned on a pledge to nationalise the mines and seize white-owned land without compensation.
On the other side of the political spectrum, the Democratic Alliance was expected to improve its vote and retain control of the Western Cape provincial government, but it still struggles to appeal to mainstream black voters.
A more complete picture of the outcome of the polls was expected by midday on Thursday.