South Africa’s President Zuma faces a motion of no-confidence as MPs vote in a secret ballot shortly.
The parliament’s speaker, Baleka Mbete, made the decision to hold the vote in secret after opposition parties took the case to the Constitutional Court.
They believe MPs from the governing African National Congress (ANC) would be more likely to vote against the president if their vote is secret.
Mr Zuma has so far survived seven no-confidence votes – none held in secret.
At least 50 out of the ANC’s 249 MPs would need to vote against the president in order for the no-confidence motion to pass.
This latest attempt to oust the president comes after he fired his widely-respected finance minister, Pravin Gordhan, in March.
This came amid accusations that the president had become too close to the wealthy Gupta family, who are accused of trying to influence politician decisions – including the sacking of Mr Gordhan.
Mr Zuma and the Guptas have denied any wrongdoing.
Protests have been taking place across South Africa ahead of the vote, with Johannesburg being one of the worst-affected areas.
Johannesburg Metro Police Department is on high alert, the city’s Councillor for Public Safety, Michael Sun, said in a statement.
Mr Zuma is due to step down as head of the ANC in December, ahead of the 2019 general election.
He has endorsed his ex-wife, Nkosazana Dlamini-Zuma to succeed him.
Also vying for the leadership is Cyril Ramaphosa, a former trade unionist and one of South Africa’s wealthiest politicians.
The decision to hold a secret ballot has surprised many and injects a new element of uncertainty into the proceedings against the president, reports the BBC’s Nomsa Maseko in Cape Town.
The question now is whether enough ANC MPs are prepared to make a stand against the president, she adds.
ANC MP Makhosi Khoza was given security protection last month after she received deaths threats for saying she would vote against the president, calling him “a disgrace”.
Meanwhile, the opposition Democratic Alliance (DA) has urged ANC MPs to “vote with their conscience”.
The party’s leader, Mmusi Maimane, told journalists that with a secret ballot, they “have no excuse”.
The ANC has described the no-confidence motion as a “political ploy” designed to remove the government “outside of general elections”.