NAIROBI, Kenya -- A slow ballot count in Kenya's presidential vote raised questions Tuesday about the election process, but it was a decision on the more than 325,000 rejected ballots that made it appear likely the election will be decided in a runoff.
Nearly 330,000 ballots -- the number keeps rising -- have been rejected for not following election rules, raising criticism of voter education efforts.
The election commission chairman announced late Tuesday that those spoiled ballots, as they are called here, will count in the overall vote total. That makes it very difficult, given the tight race, for either top candidate to reach the 50 percent mark needed to win outright. A runoff election between the top two candidates is expected.
Kenya's 2010 constitution -- passed after 2007-08 election violence killed more than 1,000 people -- says a candidate wins the presidency if he or she has "more than half of all votes cast in the election." That clause made the decision on the definition of "cast" key.
Partial returns Tuesday showed an early lead for Deputy Prime Minister Uhuru Kenyatta, the son of Kenya's founding president and who faces charges at the International Criminal Court. That prompted the camp of candidate Prime Minster Raila Odinga to hold a news conference to tell supporters that more of their strongholds have yet to be counted from Monday's largely peaceful vote.
Returns for most of the day showed Kenyatta with 53 percent and Odinga with 42 percent. But Kenyatta's percentage is likely to drop after the decision on rejected votes. The commission said percentages would be updated Wednesday.
More than half of the votes cast have yet to be counted, and observers said Odinga was likely to make gains.
"If Odinga's performance improves, as seems likely, and with this decision on the rejected votes, then it's inevitable there will be a runoff," said Nic Cheeseman, a lecturer in African politics at Oxford University who is an official observer of the election.
Kenya is the lynchpin of East Africa's economy and plays a vital security role in the fight against Somali militants. The U.S. Embassy in Kenya is the largest in Africa, indicating this country's importance to U.S. foreign policy.
The chairman of the election commission, Isaak Hassan, met with political parties Tuesday to talk about the rejected ballot issue, said Tabitha Mutemi, a spokeswoman for the commission.
Hassan acknowledged what he called "growing concern" over the slow pace of elections results. He said the delays are due to high voter turnout, a large number of contested seats and long travel times for polling officers.
Candidates' percentages, he said, will be calculated "based on total votes cast." Of the rejected ballots, he said: "Of course they will have an impact in the overall result."
Hassan noted the law gives his commission seven days to perform its work, and he asked for patience "from the public, the political parties as well as the candidates."
Kenya's Vice President Kalonzo Musyoka, who is also Odinga's running mate, held an afternoon news conference -- the first by any of the major candidates -- to calm Odinga supporters who were forced to look at TV news reports of Kenyatta's lead all day.
"We wish to appeal for calm and call on our supporters to relax, because we are confident that when all votes are in (we) will carry the day," said Musyoka.
Musyoka said more Kenyatta strongholds were counted Tuesday, meaning Odinga's vote total would rise as more ballots came in.
A European election observer gave credence to Musyoka's claim, saying an electoral analysis done by the U.S. Embassy showed that Odinga was likely to gain ground as more votes came in. The observer said he was not allowed to be identified by name.
A U.S. Embassy spokesman said the embassy did not have any comment.
Long lines of voters formed around the country Monday. Election officials estimate that turnout was about 70 percent of 14 million registered voters. Attacks by separatists on the coast killed 19 people, and other attacks were seen near the border with Somalia, but the vast majority of the country voted in peace.
In the coastal city of Mombasa on Tuesday, three suspected members of the secessionist group Mombasa Republican Council were charged in court for the murder of four police officers during elections.
Also on Tuesday, grenade blasts hit two areas -- the Somali section of Nairobi and a vote tally center in Mandera, near the Somali border. Minor injuries, but no deaths, were reported.
The leading candidate, Kenyatta, faces charges at the International Criminal Court on allegations he helped orchestrate postelection violence in 2007-08, when more than 1,000 people were killed.
The U.S. has warned of "consequences" if Kenyatta is to win, as have several European countries. Because Kenyatta is an ICC indictee, the U.S. and Europe have said they might have to limit contact with him, even if he is president.
After Kenyan President Mwai Kibaki was hastily named the winner of Kenya's 2007 vote, supporters of Odinga took to the streets in protest, a response that began two months of tribe-on-tribe attacks. In addition to the more than 1,000 deaths, more than 600,000 people were forced from their homes.
Officials have been working to ensure that level of violence does not return this election cycle. Both Kenyatta and Odinga have pledged to accept the results of a freely contested vote.
Kenyan residents appeared to approve of the electoral process so far. The election commission is giving televised press conferences and TV stations are showing the commission's frequently updated vote tallies.
"It is better managed than the 2007 elections," said Judith Egesa, 24, who works at a food shop in Mombasa. "Whoever wins the presidency, we will accept him as long he leads Kenya without tribalism and discrimination. I voted for Raila, but if Uhuru wins I have no problem provided he leads us in peace and fulfills his promises."
Associated Press reporter Tom Odula contributed from Mombasa.