Many voters want change, frustrated by corruption and skyrocketing prices, but both frontrunners vying to succeed Kenyatta have ties to the current leader.

Veteran Opposition Leader Raila Odinga has received Kenyatta's endorsement, while William Ruto has been Kenyatta's deputy president for the past decade, despite the two men falling out.

Odinga, a left-leaning former political prisoner, has previously served as prime minister and is the son of the nation's first vice president.

Ruto, a gifted orator who says he once sold chicken by the roadside, has portrayed the election as a fight between common "hustlers" and elite "dynasties".

Both are wooing voters in East Africa's richest and most stable nation by promising to reign in ballooning foreign borrowing and help the poor.

More wealth is owned by less than 0.1 per cent of Kenyans than the other 99.9 per cent combined, according to Oxfam, and the global spike in fuel and food prices has hit families hard.

The candidates have also stitched together alliances of ethnic voting blocs. Similar rivalries led to deadly violence in previous elections after results were disputed.

But unlike the past four polls, Kenyatta's Kikuyu ethnic group, the nation's largest, has no presidential candidate to unify behind, although Odinga and Ruto have each chosen a Kikuyu vice-presidential running mate.

The potential fracturing of Kenya's biggest ethnic voting bloc makes for an unpredictable election, Murithi Mutiga, Africa head for global think tank International Crisis Group, said.

"The public has grown weary of all the byzantine alliances among the political elites," he said.

"Politicians are being forced to discuss issues that really matter."

Young citizens are particularly disenchanted, he said, with many not bothering to register to vote.

Those are Kenyans like 30-year-old motorbike taxi driver Calvince Okumu, who falls into a demographic courted by both camps.

He is one of the country's 1.6 million motorcycle taxi drivers - the kind of young, hardscrabble entrepreneur Ruto promises to give loans to.

He also hails from Western Kenya, Odinga's stronghold, and could benefit from his promise to provide a basic income to the poorest families.

But he is not interested.

"Why should I line up for four hours to vote?" asked Okumu, a part-time student.

"There's no difference between the two."

The number of registered voters aged 18-34 has dropped more than five per cent since the 2017 election, despite population growth of around 12 per cent.

Okumu's more concerned about finding steady work.

More than a tenth of Kenyans aged 18-64 are unemployed, with nearly one in five out of the labour force - meaning they are not looking for work, according to the World Bank.

Endemic corruption has also angered voters; both camps include officials charged with - or even convicted of - corruption.

In the northeast, the worst drought in 40 years has left parched grazing lands and forced 4.1 million people to depend on food aid.

Their plight has barely been mentioned as would-be leaders buzzed across the country in fleets of helicopters.

The shadow of the violence following disputed 2007 elections, which killed 1200 people and displaced around 600,000, hangs over each election cycle.

Kenyatta and Ruto were among six Kenyans charged at the International Criminal Court over their alleged roles in the 2007 violence.

Both denied the charges and the cases collapsed.

Violence also followed the 2017 polls, when more than 100 people were killed.

This time, there has been less pre-election violence, with communities working hard to defuse tensions.

The Supreme Court's decision to nullify and re-run the last election also means there is higher confidence in the justice system - so disputes are more likely to be fought in court than on the streets.

Australian Associated Press