Zimbabwe`s former president Robert Mugabe was ousted by a "military coup" that forced his resignation, former cabinet minister Jonathan Moyo said in an interview with the BBC broadcast on Thursday.
Whoever wins will succeed Africa`s first elected female head of state, Ellen Johnson Sirleaf, who took over at the helm of the small west African nation in 2006.
Emmerson Mnangagwa, who took over last month from 93-year-old Robert Mugabe after the intervention of the military, is under pressure from opposition parties and the public to implement political reforms.
President Jacob Zuma, whose reign has been marred by graft scandals, will step down as ANC chief, but remain as head of state ahead of general elections in 2019.