Between 28 December, 2007, and 28 February, 2008, at least 1,000 people died and 600,000 were displaced from their homes, after President Mwai Kibaki was declared the victor and Odinga rejected the polls as rigged.
Three people were killed after an attack inside a vote tallying centre on Kenya's coast.
These suggest Mr Kenyatta is heading for a first-round victory.
Prior to Odinga's allegation on Wednesday, the leading candidates avoided using inflammatory rhetoric that could fuel tensions ahead of the vote.
And as the electoral commission finalizes its work, the country continues to wait.
Odinga said: "We fear this was exactly the reason Chris Msando was assassinated, so this could happen". He also said there had been a "serious attempt to try to either doctor or alter the final results". "We noted these efforts were directed at ensuring sufficient transparency in the presence of party agents that were at numerous polling stations", said Mahama.
The IEBC has insisted that its systems have not been hacked, while its chairman, Wafula Chebukati, on Thursday said Mudavadi's printout was riddled with arithmetic errors and came from a Microsoft database while the commission's systems run on Oracle.
What does the electoral commission say?
"You can not claim that results are fake with respect to presidential vote and you welcome the areas where your governors and MPs have won convincingly".
However, it admitted that a lack of mobile data coverage had delayed the delivery of the supporting documents, forms 34A and 34B.
The western port city on Lake Victoria has been a flashpoint in past elections.
IEBC Commissioner Roselyn Akombe said, "To enhance transparency, the commission has allowed the political party agents access to the results".
"We find ourselves at a crossroads once again", the Daily Nation newspaper warned grimly.
How did the voting go?
As of Thursday afternoon, election officials were waiting to receive about 170 forms from the country's 290 constituencies and about 1,000 forms from the 40,883 polling stations. "All of that will ultimately give confidence to people that they can trust in the outcome of the vote". "People want to see justice". One of the was young man with a massive gunshot wound to the head. The gap of over a million votes means that Uhuru has all but secured a second term in office. He won in 2013 with 50.03 percent of the vote, triggering an unsuccessful legal challenge by Odinga. If that threshold is not met, a run-off vote between the top two candidates will be triggered.
Mr Odinga's running mate, Kalonzo Musyoka, also called for restraint as the fraud allegations are investigated.
Kenya's general elections kicked off on Tuesday, with almost 20 million eligible voters expected to cast their ballots at over 40,000 polling centers to elect public officials, including the president. The case ultimately collapsed due to lack of evidence, and after key witnesses died or disappeared.