After the president resigns, the parliamentary Speaker would become acting president and the National Assembly would then have to elect a new president from its members within 30 days.
If South African lawmakers vote in favour of Tuesday’s no-confidence motion in President Jacob Zuma, he will be forced to resign along with his entire cabinet.
But the process has no precedent in South Africa, and it throws up thorny questions about the constitution and the political turmoil that would be triggered by a shock victory for his opponents.
The ruling ANC party has a large majority in the house, and would choose the incoming national leader. But the party could be torn apart by the ousting of Zuma and the debate over who should succeed him.
Analysts say that MPs might back deputy president Cyril Ramaphosa while the party’s executive might go for another candidate such as the Speaker herself, Baleka Mbete.
Ramaphosa’s main rival Nkosazana Dlamini-Zuma, Zuma’s former wife, would not be eligible as she is not a lawmaker at present.
“Passing a vote of no confidence may create chaos within the governing ANC,” constitutional law expert Pierre de Vos wrote in the Daily Maverick online news site.
Divisions between MPs and the party executive “could lead to instability and even open warfare,” he said.
A long power struggle could also ensue if the ANC executive tried to ensure victory for its preferred candidate by replacing current MPs with new loyal members.
“ANC MPs against whom action is taken would be able to approach the courts to challenge the expulsion. The process could drag on for years,” said de Vos.
The timing of the vote adds to the uncertainty, as the ANC is already entering a period of change.
Zuma is due to resign as ANC party chief in December, and he must step down as national president ahead of the 2019 general election.
If he is ousted on Tuesday, “all hell would break out within the party ahead of its conference in December,” said Roger Southall, a professor at the University of the Witwatersrand in Johannesburg.
“The ANC would be at war with itself, with little or no prospect of it facing the electorate in 2019 in one piece.”
Zuma is widely seen as preparing the ground for his ex-wife Dlamini-Zuma to succeed him as party chief in December and then as national president.
But if against the odds he was forced out of the office by the vote, all bets would be off.
Opposition parties, led by the centrist Democratic Alliance and the radical Economic Freedom Fighters, hope the turmoil could mean the once all-powerful ANC is defeated or forced into coalition in the 2019 election.