By Karen Allen BBC News, Nairobi

Kenya is facing its closet-ever election race

This is the toughest political race Kenyans have ever seen.

The big question this time round is not simply who will become the president of this booming East African economy, but whether the vote will be seen by the losing side as legitimate.

The Kenyan electoral commission says it will not release results at night, for fear of violent repercussions.

President Mwai Kibaki is fighting for a second term but he faces a tough challenge from two former cabinet colleagues - Raila Odinga from the Orange Democratic Movement (ODM) and Kalonzo Musyoka of ODM-Kenya.

Before the poll, there were allegations by opposition politicians that the president's team has hatched a plan to rig the elections using some of the 65,000 security personnel that are being deployed to keep the peace.

Although a Musyoka win does not appear to be on the cards, he could play a crucial role in shaping the next government

This has been dismissed by the president.

Three policemen were killed by a crowd in western Kenya, amid claims they were part of a plot to fiddle results.

The worry is that similar incidents will emerge as the day goes on.

Corruption concerns

So who are the main contenders standing for the presidential race?

President Kibaki swept to power in 2002 on an anti-corruption ticket.

Mr Kibaki's economic record has won him many supporters

He is credited with bringing economic growth and stability to Kenya. He has introduced free primary education and improvements in healthcare.

But his critics say he cannot be trusted and is too heavily swayed by his inner circle, known as the Mt Kenya mafia.

He has also secured the support of former President Daniel arap Moi, whose enormous wealth has helped to bankroll Mr Kibaki's campaign.

However, Mr Moi's brutal legacy and dictatorial style is bound to put some voters off.

The 76-year-old president may have put Kenya on a firm economic footing, but he has failed to tackle corruption and secure high-level prosecutions of ministers named in multi-million-dollar dodgy deals.

Many of those characters are standing for re-election and have a good chance of winning in the puzzling world of Kenyan politics.

'Authoritarian style'

Mr Kibaki reneged on a power-sharing deal with Raila Odinga, the man who secured him the top job last time round, and so Mr Odinga is standing against him now.

Mr Odinga's backers hope he can unseat the incumbent

A man with a firebrand style of politics, and a former political prisoner, Mr Odinga is the son of Kenya's first vice-president and portrays himself as a "people's president".

He comes from the Luo community of Kenya and argues that under the Kibaki administration, the fruits of economic growth eluded the poor.

Like many others, he argues that a small elite from the president's own Kikuyu tribe have gained most from economic progress and he echoes the words that so many Kenyans utter: "It's our turn to eat".

Mr Odinga has pledged greater wealth redistribution and moves to tackle corruption through the establishment of a truth and restitution commission.

Yet this is a high-risk strategy that will put him and his team in the spotlight - and that could be uncomfortable.

He is also accused of whipping up tribal tensions in a country where ethnic identity is still a defining factor.

Potential king-maker

Kalonzo Musyoka is trying to offer a third way.

Most of Mr Musyoka's support comes from Eastern Province

He has trailed third in opinion polls but claims that voters will opt for him because they are sick of ethnic tensions.

A wealthy lawyer and born-again Christian, he comes from the Kamba community with a powerbase in Kenya's Eastern Province.

Like Mr Odinga, he has a strong political pedigree, having served under Daniel arap Moi and then again under Mr Kibaki.

Although a Musyoka win does not appear to be on the cards, he could play a crucial role in shaping the next government.

With the race between Mr Odinga and Mr Kibaki being so tight, Mr Musyoka could ultimately find himself in the role of king-maker.

Fourteen million Kenyans are eligible to vote on a day which not only sees the election of a new president but also the selection of parliamentarians and civic representatives.

Thirty-thousand foreign and national election observers are monitoring the polls.

Are you taking part in the election? Text us your observations to +44 7786 20 50 85 but please remember to tell us your name and where you are.