The African National Congress took 65.9 percent of the nearly 18 million votes cast Wednesday.
The victory was never in doubt. But it was unclear whether the party would retain its coveted two-thirds of the seats in the 400-member parliament. The vote tally roughly parallels the seat distribution, but the exact number of seats must still be allotted by election officials according to a complicated formula after the final count is certified.
ANC spokesman Ishmael Mnisi said the apparent slide from previous votes was unimportant.
"We don't read much into percentages," he said. "We're quite happy with the mandate that the people of all races, black and white, have given the ANC."
The ANC won 69.69 percent of the vote in the last elections in 2004, when it was led by Zuma's rival Thabo Mbeki. It won 66.35 percent in 1999. In the country's first all-race vote in 1994, the ANC won 62.64 percent of the vote.
The party's rivals will make much of the slide, however slight.
It could be seen as a message that voters want some limits on the party. ANC rivals had argued Zuma should not have the two-thirds majority needed to enact major budgetary plans or legislation unchallenged, or to change the constitution.
"We have said that we don't need that" two-thirds majority, the ANC's Mnisi said. "We don't even have the intention to change the constitution."
It could be linked to the split in the movement that defeated apartheid. A new, black-led party formed by disgruntled former ANC leaders close to Mbeki was placed third in the race, with just over 7 percent of the final tally.
The main opposition Democratic Alliance got just over 16 percent. In total more than 77 percent of the country's record 23 million registered voters cast ballots. Turnout in 2004 was about 76 percent of more than 20 million registered voters.
A strong ethnic vote from Zulus in Zuma's rural homeland helped boost the ANC, which sees the populist Zuma as the first leader who can energize voters since the legendary Nelson Mandela. Supporters confident of an ANC victory have been celebrating since voting ended Wednesday.
Parliament elects the president in South Africa, and was expected to vote Zuma into office in May.
Zuma faces a heavy responsibility - meeting expectations for change among South Africa's impoverished black majority.
Some say Zuma is too beholden to unions and leftists, and will not be able to fulfill his promises of creating jobs and a stronger social safety net. At the end of the campaign, Zuma was talking not about creating jobs, but staving off job losses.
