President Thabo Mbeki's firing of his top deputy over corruption allegations has generated a sharp backlash among some factions of South Africa's ruling African National Congress and provoked what analysts here call the most serious political challenge to Mbeki's six-year presidency.

But some analysts say the debate over the fate of Jacob Zuma, the former deputy president, has been healthy for South African democracy and could constructively shake up a ruling party that critics say has become intolerant of dissent and inadequate in delivering services to the poor.

In the month since Zuma's dismissal, protesters supporting him have burned flags bearing images of Mbeki's face. At the ANC's national general council meeting, grass-roots activists long enchanted by Zuma's gregarious personality and populist politics sang anti-Mbeki slogans and donned T-shirts proclaiming Zuma's innocence.

Activists at the meeting also voted overwhelmingly to reject Zuma's offer to step down from his post as deputy president of the party. Supporters regarded the offer as forced by Mbeki. That left open the possibility, however slim, that Zuma might yet emerge as a formidable candidate to succeed Mbeki, who by law must step down after his second five-year term ends in 2009. That race has no clear favorite.

Analysts said the rallying on behalf of Zuma, a former liberation soldier of modest background who has strong ties with South Africa's large labor movement and the Communist Party, reflects disenchantment with Mbeki's sometimes imperious style and with the growing affluence of a group of party insiders.

Many supporters, mired in modest townships where unemployment tops 40 percent, feel left behind even as South Africa's economy has grown stronger, analysts said.

"The real grass-roots supporters, they are struggling. Things aren't getting better for them," said William Mervin Gumede, author of "Thabo Mbeki and the Battle for the Soul of the ANC." "That is the fault line now."

The recent series of outbursts were all the more startling in light of the ANC's history of disciplined and generally private debate over such emotional issues as succession. In decades of struggle against apartheid, Nelson Mandela and other ANC leaders preached the need to put the party's goals ahead of personal achievement, an ethic that has largely survived in the years since the party took power in 1994. It now controls more than two-thirds of the seats in Parliament, the presidency and the governments of all nine provinces.

Mbeki cautioned protesters in his weekly online newsletter a week ago, saying all party members needed to "conduct ourselves in a dignified manner befitting members of the African National Congress and consistent with the traditions of a movement that our people not only respect but genuinely love and admire. We must take the greatest care not to act in any manner that would compromise the image of both the Deputy President and the ANC."

The struggle was sparked by the conviction in June of Zuma's friend and financial adviser, Schabir Shaik, who, a judge ruled, solicited an $80,000 bribe on Zuma's behalf and enjoyed a "generally corrupt" relationship with him.

Two weeks later, Mbeki announced to Parliament that he was dismissing Zuma on the grounds that South Africa's fledgling democracy needed to demonstrate that even its most powerful leaders were subject to the rule of law.

Zuma's supporters reacted with rage, noting that he had not yet been charged with a crime, much less convicted. The first of the flag-burning incidents came two days later, as ANC members celebrated the anniversary of the bloody riots on June 16, 1976, that many historians regard as the beginning of the end of apartheid.

Prosecutors soon after charged Zuma with two counts of corruption, but many of his supporters maintained that he deserved to have his case heard in court before party leaders cast aside a man once widely expected to become South Africa's next president. Political analysts agree that a conviction would end Zuma's political career, and that exoneration by a court might revive it.

Some critics, however, have said the contretemps may have a broader positive effect on South African politics in general and on the ANC in particular.

Rhoda Kadalie, who writes a column for Business Day and describes herself as a "disgruntled" member of the ANC, said the party has become closed to dissent during Mbeki's presidency. She would welcome a breakup of the party, she said, as a way to pressure the ANC to refocus on delivering services to the poor, who make up much of the party's grass-roots support.

"Any split would be good for democracy. You can't have any party with 70 percent of the vote reigning over the rest of the country with a sledgehammer," Kadalie said. "What you have now is a secretive, conspiratorial clique."

But Mbeki's defenders portray the recent controversies as evidence that debate within the ANC is already healthy and freewheeling. They predict that Mbeki's decisive handling of the situation will be vindicated as tempers cool and the court case against Zuma gets underway in the months ahead. Televised images of burning flags bearing the president's visage will fade into memory, they say.

"It's an interesting question of how long the discontent you saw on television will last once people have more time to take a considered view," said Ronald Suresh Roberts, a political commentator who is writing a book on Mbeki with the president's cooperation. "People have always yelled at each other and come together. It takes [only] one man and a box of matches to burn a flag."

South African President Thabo Mbeki fired Zuma.The dismissed deputy president Jacob Zuma appeared briefly outside the court in Durban on June 29 after being charged with corruption.