What is the role of the African National Congress in the evolution of South African politics?

Put simply, the African National Congress (ANC) was
responsible for pushing South Africa away from apartheid.  The ANC's attitude under
Nelson Mandela helped to create a new South Africa after the end of the apartheid
regime.  This new South Africa is, to some extent, under threat now as the ANC seems to
be moving towards one-party rule that is hostile to
non-blacks.

When apartheid ended, the actions of Mandela
and the ANC helped to keep South Africa stable.  They did not engage in the sort of
anti-white actions that have caused so much trouble in neighboring Zimbabwe.  However,
in recent years, the ANC has seemed to be moving toward a less open and democratic
system.  It seems to be trying to take more power for itself and to demonize as racist
any opposition to its rule.  This is a worrisome development.