JOHANNESBURG — Nelson Mandela’s African National Congress once inspired hope across Africa. It helped liberate black South Africans from white-minority rule, promoting reconciliation with former oppressors and the ideal of a post-racial “Rainbow Nation.” It seemed even poised to lift up the rest of the continent with its vision of an “African Renaissance.”

But as A.N.C. members began gathering on Saturday to elect a new leader, many analysts described the still-dominant party as a shadow of what it once represented — bereft of ideals, roiled by insiders fighting over diminishing spoils, abandoned by a growing list of disillusioned graying party heroes known as “stalwarts.”

For many at home and across Africa, the once heroic liberation movement is now synonymous with corruption and cynicism. South Africa has become a normal nation.

The winner of the party election is expected to become South Africa’s next president in the 2019 elections unless the A.N.C. loses its overwhelming strength in Parliament, which selects the nation’s top executive.