First they heard about the spies. Then they heard about the secret brothels and the private planes. And the whole time, they were hearing about the assassins.

The details exposed in South Africa’s corruption scandals have upended the country’s perception of the governing party, the African National Congress, threatening its decades-long control of the government.

A generation after the end of apartheid in 1994, black South Africans are still mostly shut out of the country’s economic opportunities, while A.N.C. officials have enriched themselves largely through government contracts.