Many South Africans voice anger with him and his government over numerous issues, including high-level corruption and the failure to create jobs or provide the most basic services in gritty townships and other poor areas. When Mr. Zuma visited Malamulele in the northern Limpopo Province on Wednesday, residents jeered him as he promised to attend to their grievances, reviving memories of the boos he received at a memorial for Nelson Mandela in Soweto last December.
In Malamulele, schoolchildren ran after his motorcade shouting “Zuma sucks,” according to South African reporters at the scene.
Yet as head of the A.N.C., founded almost 102 years ago to fight for majority rights, Mr. Zuma draws enormous loyalty and political benefits. There are few if any political analysts who expect anything but a victory for him and the party in the election, in which the government faces an increasingly splintered opposition.
Still, many also expect that once Mr. Zuma is re-elected — possibly with a lower margin than the A.N.C. is accustomed to — the party will be forced into realignments reflecting a new era.
“This will be the last election in which the majority will be voting with their heart rather than their head,” said Jakkie Cilliers, head of the Institute for Security Studies, a research organization here. “It is the start of a sea change and the start of a normalization of South African politics.”
Or, as Mr. Ramaifo put it, referring to the South African leader by his initials, “I don’t think J.Z. will finish his last term. The A.N.C. will discuss replacing him.”
The election is in many ways a ballot of firsts and lasts.
The vote, scheduled for May 7, may be the last sure bet, for instance, for the generation of South African leaders including Mr. Zuma and his predecessor, Thabo Mbeki, whose credentials date from their time as exiled leaders of the liberation war against the apartheid state.
But for about a million newly registered voters, “born frees” who have no direct memory of apartheid, it will offer a first chance to pass judgment on the land to which they are heirs. The election is the first, too, since the death of Mr. Mandela.
For both voters and candidates, the ballot will be the first to reflect the impact of two of South Africa’s newest political code words: Marikana, the site of the police shooting of 34 miners on a wildcat strike for higher wages in 2012; and Nkandla, the location in rural KwaZulu-Natal of a presidential complex, complete with swimming pool, a chicken coop, a cattle enclosure and an amphitheater, that has become an emblem of the misuse of state funds.
Both words have become rallying cries for critics’ accusations that the A.N.C. has forfeited its legitimacy as a party of the people.
Above all, it will be a vote pitting an older generation surrounding the 72-year-old Mr. Zuma against newer contenders like Mmusi Maimane, 34, a provincial head of the main opposition party in Parliament, the Democratic Alliance. What is at stake, Mr. Maimane said, is “understanding that we are fighting a different battle” from the struggles of the past.
“This is a catalyst election,” Mr. Maimane said. “If nothing changes in this election, I think South Africans will look for change in a different way that could lead to instability.”
The challenges to the A.N.C. range across a broader front.
The populist Julius Malema, 33, expelled as head of the A.N.C. Youth League in 2012, is leading a new grouping called the Economic Freedom Fighters, blending a penchant for red berets in the manner of Hugo Chávez with crowd-pleasing calls for a redistribution of wealth.
This week, Ronnie Kasrils, a former intelligence minister and onetime A.N.C. stalwart, announced the “Vukani! Sidikiwe!” — “Wake up! We are fed up!” — campaign that is urging people not to vote for the A.N.C. and to look for alternatives on the ballot, or to spoil their ballot with the word “no” if they cannot find a suitable party. In the last election in 2009, almost 240,000 voters spoiled their ballots, according to official figures.
“The rot has set in with our ruling party,” said Mr. Kasrils, a former member of the A.N.C.’s Umkhonto we Sizwe guerrilla movement. “They have forgotten that they have been elected to serve the people. More and more people believe they are feathering their own nests.”
Indeed, said Vishwas Satgar, another leader of the campaign who once led the powerful South African Communist Party, a close ally of the A.N.C., in Gauteng Province, “those of us who fought in the struggle have very deep concerns where our democracy is going.”
“Our perception of the state is a crony state,” he said. “There is a crisis of legitimacy.”
“We don’t hear debate inside the A.N.C. about Nkandla and Marikana,” he added. “It’s a closing of ranks. The A.N.C. has become a patronage machine.”
The A.N.C. has responded to the Vukani campaign by calling its organizers reckless and even traitors — evidence, Mr. Kasrils argued, that “we have struck a chord.”
“We have got under the skin of the A.N.C.,” he said.
In response to the abundance of opposition groups, Mr. Zuma and his allies have sought to present an alternative narrative suggesting that over two decades in power they have begun to tackle apartheid’s uneven legacy, providing housing, electricity, running water and sanitation to big segments of the population. Recent figures from the United Nations said the murder rate, once among the world’s highest, had fallen.
In some regions, most notably his home province of KwaZulu-Natal, Mr. Zuma enjoys “celebrity status,” one reporter wrote in The Daily News, a newspaper in Durban, and the A.N.C. professes to be unconcerned about the debate around the luxurious rural compound, with its security fences and helicopter pad, at Nkandla.
In March, in the latest of many scandals swirling around the South African leader, the public protector, Thuli Madonsela, found that Mr. Zuma “benefited unduly,” in a manner “inconsistent with his office,” from state-funded improvements worth around $23 million that were supposed to enhance presidential security at Nkandla. Mr. Zuma was ordered to pay back some of the money, and he said he would respond “in due course.”
The outcome of the election is likely to be judged by the arithmetic of power. In 2009, the A.N.C. secured almost 66 percent of the votes cast. Its opponents now want to drive the share further down. Much of the battle is likely to be fought around promises of lower unemployment in one of Africa’s wealthiest nations.
“This will be my first election,” said Pretty Tsego, 19, a high school student visiting from Mpumalanga in the east of the country. “I will vote for the A.N.C. — but for the party, not the person. I’m hoping they will replace Zuma and create more job opportunities. That’s all.”