JOHANNESBURG — When South African voters last month handed the African National Congress its worst-ever losses, seemingly chastened party leaders said they would engage in “introspection.”

They promised to reach out to South Africans disillusioned by the A.N.C.’s apparent transformation from a celebrated liberation movement with cherished ideals to a corrupt party interested in self-preservation and self-enrichment.

But in the weeks since the Aug. 3 municipal elections, the A.N.C, which remains in power at the national level, has brushed aside calls from inside and outside the party to replace the scandal-tainted president, Jacob Zuma, before the end of his term in 2019. Instead of introspection, Mr. Zuma and his allies have moved aggressively to tighten their grip on the state’s coffers, surprising opponents and allies alike with their undisguised moves.

With little explanation, Mr. Zuma announced that he would directly oversee the state enterprises that have long been the source of public corruption. And his allies have renewed their attacks on Mr. Zuma’s finance minister, Pravin Gordhan, who has built a reputation for probity and has tried to uproot malfeasance in government; even one of the A.N.C.’s closest allies, the South African Communist Party, has described the moves against the minister as intended to “weaken Treasury’s struggle against corruption.”