The branches don't need to be bought for NDZ to win. Flawed and destructive thought is a ubiquitous problem in SA, paricularly amongst the ANC supporters. 
To highlight a few recent examples:

Knysna: Corporate support was generous apparently because the area is 'white.' This is contradictory to official population figures, and obviously underestimates the horror of the fire in terms of magnitude/ scale. 
Outsurance: Outrage due to lack of demographic representation in adverts.  Surely, if you are upset, close the account and sign up with a company that is more representative. 
Taxi strike: In recessionary times, losing a day in the hub of the country for an issue that ordinary folk have no role to play in was an acceptable form of protest. What of the taxi mafia? Why not exclude the middle man? 

The branches just need to be convinced that the opposing slate is pro white and pro western, and they will vote against it.  The DA loses because of this too, whilst EFF gains.