Updated

A slow ballot count in Kenya's presidential election raised questions Tuesday about the election process, but it was the more than 325,000 "spoiled ballots" that emerged as a potentially bigger issue.

More than 325,000 ballots -- a number that keeps rising -- have been thrown out for not following election rules, raising criticism of the electoral commission's voter education efforts. Those spoiled ballots, as they are called in Kenya, could still play a huge role on the election math and whether a runoff is declared for the top two candidates.

Kenya's 2010 constitution was passed after 2007-08 election violence killed more than 1,000 people and brought the country to the brink of civil war. The document says a candidate wins the presidency if he has "more than half of all votes cast in the election."

So the question is: Is a ballot that is ruled spoiled still considered to have been cast? If so, the spoiled ballots raise the total number of ballots cast, but won't add to the vote totals of any candidate, making it difficult to reach the 50 percent mark and making a runoff likely.

The chairman of the election commission, Isaak Hassan, met with political parties Tuesday to talk about the issue, said Tabitha Mutemi, a spokeswoman for the commission. She said officials would make a decision on the matter, but she did not say when.

Partial returns showed the presidential candidate who faces charges at the International Criminal Court -- Deputy Prime Minister Uhuru Kenyatta, the son of Kenya's founding president -- taking an early lead, prompting 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.

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 is larger in Kenya than any other country in Africa, indicating its importance to U.S. foreign policy.

Legal expert Ekuru Aukot helped write Kenya's 2010 constitution. He had an immediate answer on the issue of spoiled ballots.

"A spoiled ballot is considered a cast ballot," Aukot said in a phone interview. He described why some presidential ballots might be considered spoiled: for being placed in the tally box for the governor's race, for instance. "It's an administrative issue for me. That shouldn't be a spoiled ballot."

A ballot also might be considered to be spoiled if it was not stamped by a polling clerk, or if a voter filled out two choices for president, for example.

Hassan, the chairman of the Independent Electoral and Boundaries Commission, said the number of spoiled ballots was "quite worrying." Benjamin Grazda, an American election observer working for the group Sisi ni Amani Kenya -- We Are Peace Kenya -- said the high number of ballots thrown out shows voter education efforts weren't as successful as they should have been.

Hassan said political parties were pressing him to explain why the vote counting was taking so long. But he 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."

"Nobody should celebrate, nobody should complain," he said.

Returns as of Tuesday evening in Kenya -- 24 hours after polls closed -- showed Kenyatta with 53 percent of the vote and Odinga with 42 percent. Most election analysts predicted that the two would face each other again in an April runoff.

Kenya's current vice president, who is also Odinga's running mate, held an afternoon news conference -- the first by any of the major candidates -- that appeared designed 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 Vice President Kalonzo Musyoka.

Musyoka said more Kenyatta strongholds had been counted, 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 on the election.

Musyoka said the Odinga team was worried about the spoiled ballots and "we have taken very serious note of this. We have put it in writing" to the election commission. He said that failure of biometric voter identification systems also increased the chances of fraud.

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.

Kenya's capital, Nairobi, was quiet Tuesday and no more violence had been reported in the country.

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. "We want to welcome a new era. 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."