Jonathan Moyo suggested on his Twitter page last week that Mnangagwa and his deputy, Chiwengwa, could be planning to rig the vote.
"To us, it's a bunch of failures trying to come back into politics," Zanu-PF youth leader Pupurai Togarepi told the private Daily News."
Former president Robert Mugabe stepped down following a military intervention in November.
In the end, Tsvangirai’s long absence engendered a leadership crisis and void.
They have done little to honour the man who veteran Zimbabwean journalist Peta Thornycroft remembers did more than anyone.
This is seen as Mnangagwa's first step to stem graft and revive the country's moribund economy.
As the euphoria over the demise of the dictator subsides, Zimbabweans will realise the military are as much in charge under the new boss as under the old.
"The people have spoken. The voice of the people is the voice of God,” he told thousands of supporters on Wednesday.
Mugabe leaves Zimbabwe -- and the world art large -- with a powerful but tragic legacy as a destructive leader.
The worst bloodshed in Zimbabawe's recent history wasn't during the 15-year war of liberation; it came later, as Mugabe consolidated power.
Mugabe is gone, but Zanu-PF is still in power, and they are likely to protect him.
You are the proverbial hen that ate its own eggs. I am sad.
The Movement for Democratic Change party, has described the resignation of long-time leader Robert Mugabe as a "new beginning for everyone in the country".
Two of our foremost Zimbabwe experts answer your most pressing questions about events north of the border.
These are the processes involved in removing a Zimbabwean head of state.
Many are hopeful that the country will revert to constitutionalism and get to the business of the day -- the reconstruction of the Zimbabwean economy.
Zanu-PF hopes to impeach Mugabe on Tuesday, but it will need opposition support.
Zimbabwe's president Robert Mugabe, nevertheless, called for a cabinet meeting on Tuesday.
Zimbabwe president Robert Mugabe made no mention of resignation in a television address, defying his own ZANU-PF party which had sacked him hours earlier.
The international relations department said it does not comment on "party-political" matters.