Zimbabweans cast their ballots on July 30 in the country's first election since authoritarian leader Robert Mugabe was ousted past year, with concerns over fraud and the likelihood of a disputed result clouding voting day.
Stung by rejection by his predecessor former President Mugabe, who told journalists Sunday that he was not going to vote for Mnangagwa, but rather for opposition leader Chamisa, Mnangagwa released a video on Sunday imploring Zimbabweans to reject the comeback of Mugabe.
Polling stations opened at 7 a.m. (0500 GMT) and were due to close at 7 p.m. Zimbabweans are also electing 210 members of parliament and more than 9,000 councillors.
Chamisa, a 40-year-old lawyer and preacher, is facing off against 75-year-old President Emmerson Mnangagwa, a former intelligence chief and one-time ally of Mugabe.
The reported candidates are Zanu PF's Emmerson Mnangagwa and the MDC Alliance's Nelson Chamisa.
There will be a runoff on September 8 if no candidate wins more than half the votes.
GETTY FURIOUS Mugabe called the coup that toppled him'illegal and unconstitutional
Mugabe made no comment as he cast his ballot.
Chamisa, a charismatic speaker who honed his craft in the courtroom and the pulpit, has won over young and unemployed voters who are frustrated with almost four decades of Zanu-PF rule.
"Let tomorrow be the voice of the people saying this and never again ...", said the ageing former leader in apparent reference to the use of the military by Mnangagwa to come to power.
"This is a historic day", said Fabian Matsika, a security guard who woke at 4:30 a.m.to travel to his polling station on the outskirts of the capital.
Mnangagwa has welcomed foreign media and global observers from the European Union, the United States and the Commonwealth, who are watching polling stations across the country.
"However the public's faith in the secrecy of the ballot is essential for the credibility of the process". He said he wished whoever wins well.