"This is a positive feedback for us", polling official James Njaya said of the high turnout in Kibera, a poor area in Nairobi, the Kenyan capital.
There are eight candidates vying for the presidency.
Odinga alleged voting irregularities after losing to Kenyatta in the 2013 election and took his case to the Supreme Court, which ruled in Kenyatta's favour by saying the election was valid. Last week, one senior election official was found murdered, his body displaying signs of torture. More than 14,000 candidates are standing in those elections.
"Many middle-class Kenyans will, in an instant, go from speaking of globalization and borderless innovation while sipping on their cafe macchiatos to offering blind support to a well-known thug who happens to be from their tribes", journalist Daniel Kalinaki wrote in a recent column for the Daily Monitor newspaper. So what is at stake?
The president's father, Jomo Kenyatta, was Kenya's first president while Odinga's father, Jaramogi Odinga, served as his vice president.
The August 8 election is seen as a crucial test of Kenya's progress since a disputed poll a decade ago led to two months of politically motivated ethnic clashes, which along with a police crackdown on protests left more than 1,100 dead and 600,000 displaced. Previously he had been finance minister, and in 2002 he lost a historic election which ejected KANU, the party of dictator Daniel Arap Moi, from power.
Kenyans are heading to the polls on Tuesday, in a close presidential election between incumbent President Uhuru Kenyatta who seeks a second term and Raila Odinga. Mr Odinga's coalition of popular politicians from the major ethnic groups, his populist rhetoric, and the electoral reforms he successfully pushed for, could sufficiently tilt the balance in his favour.
Most political organizing in Kenya is tied to ethnicity.
Elections in 2013 were largely peaceful, although Odinga did accuse Kenyatta's Jubilee Party of poll fraud after massive glitches with the electronic voting system.
Under the new constitution passed in 2010, a presidential candidate must win a minimum of 25 percent of the votes in at least 24 of the 47 counties to secure the presidency. In his defence, Mr Kenyatta asserted the debate would have been a waste of his time, preferring as he put it, to be commissioning projects. Mr Kenyatta, who is a Kikuyu, is running with vice president William Ruto, a member of the Kalenjin tribe. The system is meant to provide accuracy and fairness in determining election results.
While in Rwanda there was little doubt that incumbent president Paul Kagame, would once again sweep the election, Kenya's elections appear to be much more competitive. There are some reasons to hope that Kenya will escape the worst.
This year more than 150,000 security force personnel have been deployed.
"I have come here to vote because good leadership comes from God".