The polls in five weeks will be the first since Zimbabwe’s veteran leader Robert Mugabe resigned following a brief military takeover in November last year after 37 years in power.
The intervention by the army was led by Chiwenga who was then head of the armed forces.
The vote will be a key test for Mnangagwa, 75, who succeeded the 94-year-old autocrat and remains untested at the ballot box.
He has pledged to hold free and fair elections as he seeks to mend international relations and have sanctions against Zimbabwe dropped.
Previous elections in Zimbabwe have been marred by electoral fraud, intimidation and violence, including the killing of scores of opposition supporters in 2008.
Mnangagwa has been accused of involvement in the Gukurahundi massacres of the 1980s that claimed the lives of around 20,000 regime opponents in the country’s southwest where Bulawayo is situated.
Twenty-three candidates –- the highest number in the country’s history — will contest the presidential race.
The main competition will be between Mnangagwa and the main opposition Movement for Democratic Change’s leader, 40-year-old Nelson Chamisa.
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