Seven political parties are meeting at Emperors Palace in Kempton Park for the next two days to thrash out a plan to unseat the ANC.
The meeting, led by the DA, is meant to come up with an agreement on future coalitions in provinces where the ruling party fails to secure an outright majority.
Having won the Western Cape, the DA believes provinces like Gauteng, KwaZulu-Natal and the Free State are up for grabs in the 2024 national and provincial elections.
The national convention made up of the DA, IFP, FF Plus, ActionSA, ISANCO, UIM and Spectrum National Party, is still short of 50% of the national vote according to the 2019 election results and election polls.
ActionSA founder Herman Mashaba said the ANC will lose its majority next year and voters will look to the opposition parties for a future government.
A pilot project of the coalition between parties opposing the ANC in KZN is working well and has reduced the ANC vote in municipalities across the province.
IFP president Velenkosini Hlabisa said voters no longer place their hopes on the ANC.
DA leader John Steenhuisen said the indaba comes after three months of negotiations and planning.
"Now, we are working to map a new transition to defeat the ANC and rescue South Africa," he said.
The gathering is a litmus test for the DA whose inability to lead stable coalitions has already cost it control of the Ekurhuleni and Johannesburg Metros.
Professor William Gumede who is the independent coordinator of the gathering said the parties will have to take all their decisions in the interest of the public.
He said they will have to forge unity of common purpose and rise above petty squabbles.
Talks of uniting the opposition have been in the making since January but a number of opposition parties are still outside the tent.
These include the UDM, ATM, the Good Party, the EFF, NFP, ACDP, Rise Mzansi and others who are all opposed to the moonshot pact drafted by the DA.
The meeting comes after a collapse of the national dialogue on coalition government called by the ANC government.
ANC spokesperson Mahlengi Bhengu said the ANC was speaking to its friends as well.
Party president Cyril Ramaphosa is due to unveil a revised manifesto of the ANC on 2 September updating the nation about plans to address the energy crisis, unemployment and poverty.