Democratic Alliance (DA) chief whip John Steenhuisen does not expect his party's motion of no confidence in President Jacob Zuma to succeed, but expects it to be a turning point.

"I believe the ANC [African National Congress] will back President Jacob Zuma on the day," he told a gathering of young professionals at a Let's Talk Cape Town event on Thursday evening.

"But it will really be a turning point," he said of the motion, scheduled for August 8.

He expected some MPs to break rank. Even if one ANC MP voted for the motion, it would be a "mortal wound" for Zuma, as the false facade of unity in the party would be broken.

The South African Communist Party (SACP) had called on Zuma to step down. It recently announced it would contest elections under its hammer and sickle symbol, rather than under the ANC's shield and spear.

ANC MP Makhosi Khoza said she would vote with her conscience and called for a secret ballot. She received death threats for doing so, and for her criticism of the ANC and its leadership.

Steenhuisen said it would be interesting to see which ANC MPs were absent or abstained, and how the SACP members in the ANC behaved.

"I think we are still going to be stuck with Jacob Zuma on the 9th, but he'll celebrate Women's Day weakened."

Steenhuisen did not think National Assembly Speaker Baleka Mbete would allow a secret ballot.

"She has never put the Constitution and the people first."

He expected her to make her decision on the secret ballot known at the last minute, as part of her "game plan" to ensure the House descended into chaos on the day.

Steenhuisen said it would probably be to the DA's political advantage if Zuma stayed in power until 2019, but that it was more important to put the country's interests first.

He expected a coalition government after the 2019 general election. He said it would be the first since 1994 where the outcome was not a foregone conclusion. A coalition government could work, but it would not be easy, he said.