Record electoral losses and deep internal divisions are threatening both the long hold on power enjoyed by South Africa's ruling ANC party and the political future of President Jacob Zuma.
Since 1994, the African National Congress - once led by Nelson Mandela - has comfortably swept to victory in elections, and remains the largest party in the country.
But in last month's municipal elections, the loss of control of the capital city Pretoria, economic hub Johannesburg and port city Port Elizabeth point to the party's new fragility.
"The ANC is being consumed by three demons - corruption, factionalism and a leadership without credibility," Prince Mashele, analyst and co-author of "The Fall of the ANC: What Next?", told AFP.
The party has always bred factions and divisions, but its dismal showing during the August 3 local elections has brought tensions to the surface.
On Monday, activists from rival party factions scuffled in downtown Johannesburg as anti-Zuma members threatened to occupy the party's headquarters.
"This is certainly the first time it has come to the fore in such a widely expressed way," said Mari Harris, an analyst and director of Ipsos pollsters in South Africa.
Despite the increasingly vocal calls for Zuma to step down, many experts caution that he retains a strong grip on the party's power structure and draws loyalty from his extensive patronage network.
"There are two extremes within the party - pro and anti Zuma - but in between there are other people who tolerate the president for now," said Harris.
The party is due to choose a new leader at the end of next year, with the selected name then running as president in national elections in 2019 when Zuma cannot stand for a third term in office.
"What we are witnessing now is not the end, it's part of a downward spiral to the bottom," said Mashele.
"The bottom eventually will be when the ANC is totally removed from power and we are not yet there."
Several analysts forecast support for the ANC - the celebrated party that freed the country from apartheid - dipping below 50 per cent in the 2019 election.
Public frustration has grown over its failure to tackle the country's modern problems of soaring unemployment, low growth and little real change for many of the poorest since the end of white-minority rule.