After failing to impeach the president, opposition leaders said they would use street protests and other means to keep the pressure on Mr. Zuma. On Wednesday, in a sign of widening popular discontent, an umbrella group of leaders from churches, unions, academia and other institutions said they would begin a campaign to press Mr. Zuma to step down.

But within the A.N.C., there has been only a trickle of calls for Mr. Zuma’s resignation, coming from a few retired, though prominent, officials.

In comments widely interpreted as being directed against Mr. Zuma, David Makhura, a party member and the premier of Gauteng, the province that includes Johannesburg and is the nation’s richest and most urban, said this week that loyalty to the country was more important than loyalty to the party. In November, Mr. Zuma said the A.N.C. was more important than South Africa, refusing to retract his statement after it elicited widespread criticism.

“When the A.N.C. was going to consider what next to do, we knew that the A.N.C. would act in the best interest of the people and the country,” Mr. Makhura said at a memorial service for a party veteran. “We should ask ourselves whether we can still say that today.”

The A.N.C. chapter in Gauteng Province has not backed Mr. Zuma as the party’s presidential candidate in the past. Voters, especially in Johannesburg, the provincial capital and the country’s largest city, have gravitated to opposition parties in recent elections. For the first time since the end of apartheid in 1994, the A.N.C. is expected to face serious challenges in Johannesburg and some other cities in local elections scheduled for August.

The split inside the A.N.C. reflects wider cleavages inside South Africa itself, said Steven Friedman, a political analyst at the University of Johannesburg.

In urban pockets, a growing black middle class, participating in the formal economy, looks to politicians for good government, Mr. Friedman said. These include A.N.C. members who are opposed to Mr. Zuma and his politics.