Alexandra Township, South Africa (CNN) Simpiwe Madau wears his loyalty on his sleeve, strolling down First Avenue in a faded black shirt bearing the message: "I am ANC."

And, in a way, he is. Like his father before him, Madau is a mobilizer for South Africa's ruling ANC party here in Alexandra, a wedge of informal settlements, government housing, and dusty industry in north Johannesburg.

During elections, he cajoles people on his shack-filled street to vote for the party. On off years, he acts as a kind of informal community liaison.

Madau and thousands like him are the dependable foot soldiers of the party, pointing to its achievements like providing housing, water, and government grants to the residents of Alexandra.

But these are strange times for the party of Nelson Mandela. And lately, the ANC is a hard sell. Nowadays, all everybody wants to talk about is Jacob Zuma.

This week the embattled South African president faces perhaps his toughest test yet: a vote of no confidence -- by secret ballot -- in parliament.

And even party devotees are turning against him.

"It's all about Zuma," says Madau. "If he still loves this organization and if he still loves the country, then he should do the honorable thing and step down for the good of the country."

No stranger to scandals

Jacob Zuma is no stranger to criticism and scandals.

In 2016, South Africa's top court ruled that Zuma had acted unconstitutionally when he used $15 million in public funds to upgrade his private home, and ordered him to repay some of the money.

Zuma, 75, denies the corruption allegations against him. And despite street protests, opposition maneuvering , and defections from his own party, he refuses to step down.

On Tuesday, lawmakers from the opposition Democratic Alliance (DA), will lead a no confidence motion against him. If they can secure a simple majority, Zuma and his entire cabinet will be forced to resign.

DA leader Mmusi Maimane says the time has come to challenge the President: "I think there is a collection of South Africans from all walks that are now standing together when you start to get rid of Zuma."

For the motion to succeed, at least 60 ANC MPs will have to turn their backs on Zuma and join forces with the opposition.

Speaker Baleka Mbete announced Monday afternoon that the no confidence vote would be by secret ballot -- a move likely to severely test the loyalties of a party already wracked by infighting.

ANC chief whip Jackson Mthembu warned last week that voting in favor of the motion would be like "throwing a nuclear bomb at the country."

Fresh corruption allegations

In the past, the ANC has always managed to close ranks when faced with internal division, but a new spate of corruption allegations has severely tested Africa's oldest liberation movement.

Zuma and his closest supporters already stood accused of having questionable links with the Guptas -- a wealthy expat Indian family with vast business interests in South Africa -- after an official report by the former public protector, an anti-corruption watchdog, found evidence of possible government corruption and recommended an official inquiry.

Zuma and the Guptas denied the allegations in last year's report.

But a recent leak of more than 200,000 emails suggests corruption on a far wider scale -- implicating cabinet members, state-owned industry executives, and members of Zuma's own family.

"There are real concerns that the president and those closest to him have undermined those institutions, that they have captured those institutions and they have effectively paralyzed them so that they are too scared to act," said Susan Comrie, an investigative journalist with AmaBhungane, the non-profit group that exposed the emails

"Once you start digging and you start investigating, you don't really know where it's going to end," Comrie adds.

Zuma has denied a corrupt relationship with the Guptas from the beginning; he called for the emails' veracity to be investigated by an inquiry, but has yet to launch one.

Through their lawyer, the Guptas have called the emails "fake news."

The ANC has welcomed an inquiry into the allegations by the new public protector.

Tough choice for ANC lawmakers

Even with a secret ballot, the vote of no confidence could be a long shot.

ANC politicians are already looking to a future without Zuma. The party will meet in December to choose his successor. Many in the ANC would rather dictate their own future than be led by opposition groups.

But several powerful ANC members, like former finance minister Pravin Gordhan, who was controversially sacked by Zuma earlier this year, have called on MPs to vote their conscience.

The party has already paid a political price for supporting an unpopular president, suffering substantial electoral losses in the last nationwide election.

Outside politics -- or perhaps because of it -- the South African economy is struggling. Earlier this year the country entered its second recession in seven years. Unemployment is staggeringly high for the nation's youth. Certain types of violent crime are on the increase.

And with each new corruption revelation, it becomes harder for the ANC to stand by Zuma.

The party's MPs will face a difficult decision in the no confidence vote.

But for Madau in Alexandra, the equation is simpler. He says the ANC must choose between what is good for South Africa, and what is good for the president.

"Corruption is demoralizing this country," he says.

This story has been updated to correct the year that the Constitutional Court ordered Zuma to repay public funds over house improvements, and the amount he was ordered to pay.