African National Congress seeks to win back metropolitan areas lost to opposition-led coalitions in 2016, including respective political and commercial capitals Pretoria and Johannesburg.
South Africans cast ballots in local elections expected to reflect growing discontent with the African National Congress, whose popularity has been waning even before deadly riots in July.
Polls suggest a majority of voters on Monday could for the first time turn against the ANC, which has governed nationally since Nelson Mandela's election ended white rule in 1994.
Polls opened at 0500 GMT and are scheduled to close at 1900 GMT.
High-placed party members, including ex-president Jacob Zuma, face a slew of corruption investigations - the latest linked to coronavirus spending.
Unemployment has hit 34.4 percent. In July, Zuma's imprisonment sparked riots and looting that left at least 354 dead.
But for many voters, daily frustrations are at the forefront. Decades of mismanagement have corroded state utilities, causing water cuts and rolling blackouts that interrupted the ANC's own campaigning.
About 26 million people registered to vote, out of an eligible population of around 40 million.
They will be choosing local councillors in 257 municipalities.
Ramaphosa and other top ANC leaders have relentlessly campaigned across the country, with the president himself even stumping in small towns.
In 2016, the party won just under 54 percent of the vote nationally, its worst electoral setback ever.
Throughout the campaign Ramaphosa has been trying to convince voters that they are "cleaning up the party".
A record 1,700 of the 60,000 candidates in Monday's races are independents, reflecting disenchantment with the mainstream parties.