Minutes after the swearing-in, he faced questions about corruption and political killings in his province. “There’s nothing to set straight,” he told the national public broadcaster.

“I’m here to serve South Africans,” he added. “Let’s give this government a chance.”

He beamed: He now served under President Ramaphosa, who had served under President Zuma, who had served under President Thabo Mbeki, who had served under President Mandela. All of them, except for Mr. Mandela, were forced out by their successors.

Asked whether Mr. Mabuza would lead the nation one day, Ms. Mhaule, his former education minister, sounded confident.

“He may,” she said. “He will. Not he may, he will.”

As Mr. Ramaphosa, who declined to be interviewed, struggles to unite the A.N.C. and overcome corruption, Mr. Mabuza has vowed to “protect” the president.

“He is very safe with me next to him,” Mr. Mabuza has said.

But back in Mr. Mabuza’s province, the government is in trouble. The two biggest departments in the budget — education and health — are plagued by mismanagement, the National Treasury says. The health department is at risk of being taken over by the provincial treasury. Political killings have resumed.

“The center does not hold anymore,” said Mr. Sedibe, the former A.N.C. leader.

In June, residents furious over poor government services set four schools on fire.

“Where are the children going to learn?” asked Sdudla Mlambo in a township called Matsulu.

The night before, a fire tore through six classrooms in her granddaughter’s school. Yellow tape cordoned off the site.