JOHANNESBURG — South Africa’s ruling African National Congress will meet on Dec. 16 to elect a new party president. It will do so in the throes of a debilitating crisis. A decade of President Jacob Zuma’s leadership has seen Africa’s oldest liberation movement become a caricature of corruption and factionalism.

The A.N.C.’s electoral support is in steep decline. In the 2016 municipal elections it lost control of the capital city Pretoria, as well as South Africa’s economic powerhouse, Johannesburg. Its historical alliance with the South African Communist Party is all but dead. The Congress of South African Trade Unions, its other partner, is in deep crisis. It is unlikely that the A.N.C. will win the 2019 national and provincial elections outright.

At the center of the party’s troubles is a business family, the Guptas. Led by three brothers — Ajay Gupta, Atul Gupta and Rajesh Gupta — the family moved to South Africa in 1993 from Saharanpur, a small, impoverished town in the northern Indian state of Uttar Pradesh.

When the Guptas arrived in South Africa, they astutely acquired citizenship as naturalized “blacks” to benefit from the country’s black economic empowerment laws. The Guptas, who started their South African life with a computer business, befriended and employed President Zuma’s son, Duduzane Zuma, and eventually appointed him a director of one of their companies.