Zuma's ANC, which now controls the majority of the country's 278 municipalities, has been weakened by graft scandals and growing public discontent since it led the fight against white-minority rule.
At a massive final rally, the party made a last push for votes, stressing its anti-apartheid history and past accomplishments.
"Millions of our people must vote ANC and enable their movement to continue improving the lives of our people," Zuma told a packed Ellis Park Stadium in the Johannesburg city centre.
An estimated 55,000 supporters decked in the ANC's green, yellow and black filled the stands for the extravagant rally in a campaign the party said had cost it R1 billion ($72 million).
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"We have walked the streets of this country, we have visited every town, every city. We have been to thousands of homes," said Zuma.
The latest Ipsos opinion polls suggest that the ANC, which has ruled since the end of apartheid in 1994, could be under threat in three major cities -- Pretoria, Johannesburg and Port Elizabeth -- in Wednesday's election.
The main opposition Democratic Alliance (DA), which rules in Cape Town, is hoping for a breakthrough result, citing the country's poor economic performance and a series of corruption scandals plaguing Zuma.
"A lot of money was wasted there that should have been spent on the people," Frieda Motlatla, 24, told AFP at today's rally.
But with her hair wrapped in an ANC turban, she said Zuma's troubles would not affect her support: "I don't vote for a person, I for a party."
"Nkandla is not our business," agreed Simon Machaka, 42. "Some people will always be dissatisfied. They don't focus on the good things."