I really doubt whether he needs to rig the elections. The ANC remains immensely popular among the ethnic Africans (who are around 80% of the total population). And despite the election of Mmusi Maimane as the head of the opposition DA party, most of the Africans regard that party as white-dominated.
The problem though is that in our last elections the ANC lost 3 metros. They are a 105 year old liberation party and they will not be letting go soon.
Every time we try a Motion Of No Confidence, Baleka Mbete, the speaker of the house refuses a secret vote. The secret vote is what we need in order for the "true ANC members" the ones who believe in the right thing to do, to have a vote that would...
a. Not lose their jobs.
b. Not risk their lives.
If a Vote Of No Confidence were to go through, ALL of his cabinet crooks would fall with him too and that is what they fear the most because the vast majority of them are tenderpreneurs, siphoning off whatever tender they can get for their own benefits.
The African National Congress (ANC) of South Africa is very similar to the Indian National Congress (INC) of India. The INC managed to rule India for many decades, despite the rampant corruption and nepotism. The people voted for them, just because they were the party of liberation. But look at their condition now. The INC was demolished during the 2014 elections. They got just 44 seats out of 543. The same is going to happen to the ANC, if they take their voters for granted.