Prime Minister Raila Odinga, locked in a tight race against Uhuru Kenyatta, told Reuters he was still confident of a first-round victory, but his comments hint at legal wrangles and tension if the result is as close as surveys suggest.
More than 1 200 people died in ethnic violence in 2007 after Odinga disputed the victory of incumbent president Mwai Kibaki.
Speaking on the last day of campaigning, Odinga said the election committee had failed to register all voters in his core constituencies but not in areas viewed as heartlands of Kenyatta's. But he said that, unlike in 2007, he had confidence
in a reformed judiciary to adjudicate.
If he sought to raise a challenge, Odinga said, "we will go to court and we will urge our people to be calm and peaceful and await the outcome of the petition".
For years seen as one of Africa's most stable democracies, East Africa's biggest economy is being watched by African and Western donors and investors to see if it can now hold a vote where disputes are played out in court, not on the streets.
Although the new Independent Electoral and Boundaries Commission (IEBC), which denies any bias, is widely seen as much more impartial than its predecessor, and reforms have made the judiciary less political, many ordinary Kenyans are preparing
for the possibility of violence.
In an hour-long interview, Odinga, scion of a family at the heart of Kenyan politics since independence in 1963, said he still expected to win more than 50% of the vote on Monday, avoiding the need for a run-off.
"We still don't think that all these reports [of shortcomings in preparations] will have much impact to the outcome of elections," said the 68-year-old, who may now have his last chance to secure the top job.
"We have urged the people to turn out and vote in large numbers."
Five years ago, 350 000 people fled their homes when rival ethnic groups fought with machetes, knives and bows and arrows.
In the areas that were worst affected, many store owners are again running down stocks for fear of new carnage.
Residents of some ethnically mixed areas have returned to their tribal homelands, many of them prompted by threatening leaflets.
Odinga said the election commission had failed to send enough biometric registration kits to strongholds of his Coalition for Reform and Democracy (Cord), so that his supporters were under-represented on voter lists.
"Rigging of an election is not just on the polling date," Odinga said.
"I don't know whether it is by design or by omission."
IEBC chief executive James Oswago denied the charges but said some politicians were better at drumming up registration.
He said the 30-day registration period had not been extended, which Odinga said he had requested, because of a tight schedule.
"The same formula was applied in his areas as we applied elsewhere," he told Reuters.
Speaking in the lush garden of his villa in the Karen suburb on the outskirts of Nairobi before heading out for a final rally, Odinga said some four million people who should have been on voter lists had been left off, although he did not say how many he viewed as his backers.
About 14-million Kenyans have been registered to vote.
Odinga also accused his opponents of using the civil service to promote their parties or of using food aid to win support, allegations that they deny.
Regarding his main rival, Odinga said many voters appreciated "the danger" of electing Kenyatta and his running mate, Williams Ruto, both charged by the International Criminal Court (ICC) with orchestrating violence after the 2007 vote.
The United States and Western countries worry about future ties if Kenyatta wins the race to lead Kenya, a major recipient of aid and a regional ally in the fight against militant Islam.
Odinga also said some Kenyans might sympathise with Kenyatta and Ruto, who "portray themselves as innocent victims".
Both men deny all the charges.
Odinga, who has previously quipped that Kenyatta would have to run a government by Skype from The Hague, said if he won the election he would petition the UN Security Council to have the cases referred back to Kenyan jurisdiction.
Typically for a Kenyan election, tribal loyalties will trump ideology for many.
Odinga, from the Luo tribe, and Kenyatta, a Kikuyu, will need to reach beyond their tribal heartlands if they are to win with more than 50% of the vote. Both have picked running mates from other ethnic backgrounds.
Odinga pledged to weed out corruption from the civil service, where Kenyans complain of a culture that runs from small-time bribery to multimillion-dollar scams.
He said he would extend to government the reforms that have begun restoring trust in the judiciary and police by making them less susceptible to political interference.
He also promised to deal fairly in adjudicating land disputes, in line with the 2010 Constitution. Many Kenyans have long resented seeing politicians carve up
vast tracts of land, leaving the legions of smallholders who are the backbone of Kenyan agriculture struggling for a profit on smaller and smaller farms. - Reuters