But Mr. Ramaphosa (pronounced rah-mah-POH-sah) had remained largely silent about corruption during the three years he served as Mr. Zuma’s deputy.
In the two-week-long political crisis that led to Mr. Zuma’s forced resignation on Wednesday, party leaders waved away any suggestion that they wanted Mr. Zuma out because of his scandal-ridden administration and troubling behavior.
Ace Magashule, the party’s secretary general, said emphatically earlier in the week that the former president had “not been found guilty by any court of law” and had not “done anything wrong.”
Mr. Zuma himself complained that party leaders, in demanding his resignation, gave him no explanation.
“I have only asked my party to articulate my transgressions,” he said in his resignation address to the nation, clearly aware that it was loath to do so.
Mr. Zuma said he had not been “the epitome of perfection.” But he added pointedly: “If truth be told, none of us are.”
In fact, Mr. Magashule, the A.N.C. official, has been implicated in cases involving the misuse of public funds in his home province.
“It’s a legitimate question that Zuma asked,” said Lawson Naidoo, executive secretary of Council for the Advancement of the South African Constitution, “and it’s a question that the A.N.C. needs to answer, because they have also failed the people of South Africa by failing to hold their own president to account.”
“What we’ve seen in the last few days is the A.N.C.’s own chickens coming home to roost,” he said.
Mr. Ramaphosa began speaking out against corruption last year as he campaigned for the leadership of the A.N.C. After his victory in December, Mr. Ramaphosa and his allies pressed Mr. Zuma to form a commission of inquiry into influence-peddling in his administration.
The High Court had ordered Mr. Zuma to do just that, but Mr. Zuma, in a continuing bid to block the inquiry, had been preparing an appeal.
“There is commitment to fight corruption in the new government,” said Mcebisi Ndletyana, a political professor at the University of Johannesburg. “Whether or not it is lasting, that is for the future to tell.”
“In the course of the investigation,” Mr. Ndletyana said, referring to the inquiry into influence-peddling, “you’ll be stepping on powerful toes.”
“You might even embarrass the party,” he added. “Some money might have made it into party coffers. All sorts of concerns start kicking in and the investigation might be stifled.”
The nation’s highest court found Mr. Zuma guilty of violating the Constitution in a corruption case related to his homestead, Nkandla. In addition to the public inquiry on influence-peddling, he could also face charges related to an arms deal from the 1990s before he became president.
Mr. Ramaphosa is expected to serve out the remainder of Mr. Zuma’s term, which ends in mid-2019, and will be eligible to run for two full terms after that. In Cape Town, where Mr. Ramaphosa was elected in Parliament, the change in leaders brought hope to some voters.
Mfanufikile Zulu, 32, from a family of A.N.C. supporters, said that under Mr. Zuma, “it was like the A.N.C. was falling apart.” He added, “It was very difficult for us.”
“What matters now is for the A.N.C. to resolve its problems,” he continued, saying that he had faith in Mr. Ramaphosa. “He won’t let the country go down.”
But others expressed skepticism about the recent developments inside the ruling party — a power struggle between two factions that took place out of the public eye among a few individuals.
“I won’t be encouraged by the new leadership until I see them taking action,” said Goodness Mkhize, 75, a retired schoolteacher and nurse, adding that Mr. Ramaphosa “was also part of everything that’s been happening in the A.N.C.”
“He can’t just go to sleep tonight and wake up a new person tomorrow,” she said. “How is he going to change things he’s been part of for so long?’’