The claims pointed to a contested result in the historic election, raising the prospect of competing fraud allegations and a possible run-off vote in September - required if no candidate wins at least 50 percent of ballots in the first round.
But he re-surfaced unexpectedly on the eve of the election, holding a rambling two-hour press conference to announce that he would not vote for his successor Emmerson Mnangagwa and the ZANU-PF, complaining they had "tormented" him.
"Social media makes the landscape tricky".
People queue in order to cast their ballot outside a polling station located in the suburb of Mbare in Zimbabwe's capital Harare, on July 30, 2018.
With 5.6 million registered voters, full results of the presidential, parliamentary and local elections are due by August 4.
In much of Harare, the mood is quiet. After voting, Chamisa said his victory is a foregone conclusion.
Zimbabwe's opposition party has declared that their presidential candidate Nelson Chamisa won yesterday's election, despite no official results being released.
Mnangagwa was viewed as the front runner, although the latest opinion polls showed a tight race.
His rule was tainted by corruption, mismanagement and diplomatic isolation.
That will leave little scope to improve government services, rebuild crumbling transport links and meet a plethora of other election pledges.
Zanu-PF deputy legal secretary and former deputy justice minister Fortune Chasi told VOA that, "Mr. Mnangagwa announced on Saturday that he had finished his campaign when he addressed a rally at the National Sports Stadium in Harare".
The analyst said peace and political stability in Zimbabwe would bring stability to its neighbouring countries suffering the burden of economic migrants and asylum seekers who moved to the Southern African Development Community (SADC) countries.
"A peaceful, free and fair election that is universally accepted as credible by foreign observers and establishes a strong enough political mandate domestically to commit to hard fiscal cuts is the ideal outcome".
Hundreds of worldwide observers have been deployed to ensure the vote goes smoothly, but the opposition has repeatedly alleged irregularities in the voter roll.
There were no immediate reports of violence, said Andrew Makoni, chairman of the Zimbabwe Election Support Network, an association of 34 civil rights and religious organizations. "Waiting patiently for official results as per the constitution".
Mugabe defended Zimbabwe's election commission after Chamisa and the opposition raised concerns that the vote will be flawed, saying that "it acts quite freely".
This morning both candidates were confident what today's results was going be.
The MDC was able to access rural districts that were once no-go areas, but it's still skeptical the election will be fair.
People had to re-register for this year's poll as the electoral commission introduced a biometric system to eliminate any "ghost voters" - though the opposition still alleges there are irregularities in the voters' roll.
Mnangagwa has insisted the election will be credible.
Several worldwide observers said the voting process had been slow at some stations, but it did not appear to them to be intentional.
"Now we need the final count from the Zimbabwe Electoral Commission". I mean, they are just perpetuating their bias.