KHUTSONG, South Africa — The party that ended apartheid has begun to lose its appeal among black South Africans, many of whom have grown frustrated waiting for the ‘‘better life for all’’ promised when the African National Congress won historic multiracial elections 18 years ago.

The disenchantment with the ANC, to be sure, has been gradually building over the years. But it has intensified in recent weeks amid ongoing, and often violent, labor unrest that has spread across the nation since police killed 34 strikers at a platinum mine in August, the deadliest police action in post-apartheid South Africa.