Supporters of Kenya s Azimio La Umoja Party (One Kenya Coalition Party) presidential candidate Raila Odinga sing as they gather outside the Milimani High Court in Nairobi on August 22, 2022, as they wait to file a petition against the result of the recent general election. AFP
Odinga, a veteran opposition leader who ran with the backing of the ruling party, has rejected the outcome of the poll, branding it a "travesty", after he narrowly lost to Ruto by around 230,000 votes or less than two percentage points.
"It has already been sent to them and they will see it soon," said Daniel Maanzo, who is part of the 77-year-old politician's legal team.
"We have hopes that we have made a good case and will win," he said.
Paul Mwangi, who is also representing Odinga, told AFP that a physical copy of the petition would be filed before the Supreme Court's 2 pm (1100 GMT) deadline.
Although polling day passed off peacefully, the announcement of the results a week ago sparked angry protests in some Odinga strongholds and there are fears that a drawn-out dispute may lead to violence in a country with a history of post-poll unrest.
Since 2002, every presidential election in Kenya has triggered a dispute, with this year's outcome also causing a rift within the Independent Electoral and Boundaries Commission (IEBC) that oversaw the poll.
Odinga, who was making his fifth bid for the top job, also approached the Supreme Court in August 2017, when President Uhuru Kenyatta was declared the winner of the presidential race.
'Null and void'
The court annulled that election in a first for Africa and ordered a re-run which was boycotted by Odinga. Dozens of people died during a police crackdown on protests.
Judges now have 14 days to issue a ruling. If they order an annulment, a new vote must be held within 60 days.
Odinga, who has since buried the hatchet with Kenyatta, winning the president's backing for his candidacy, said last week that the figures announced by the IEBC were "null and void and must be quashed by a court of law".
The IEBC was under heavy pressure to deliver a clean vote after facing sharp criticism over its handling of the August 2017 election.
But in a shocking development shortly after the results were announced, four of the IEBC's seven commissioners said the numbers did not add up, accusing chairman Wafula Chebukati of running an "opaque" operation.
Chebukati dismissed the allegations, insisting that he had carried out his duties according to the law of the land despite "intimidation and harassment".
Legal experts are divided on whether Chebukati needed the commissioners' backing to announce the results, with constitutional lawyer Charles Kanjama telling AFP there was "some ambiguity" surrounding the issue.
Odinga has previously said he was cheated of victory in the 2007, 2013 and 2017 elections, and the poll's aftermath is being keenly watched as a test of democratic maturity in the East African powerhouse.
On the campaign trail, both frontrunners pledged to resolve any disputes in court rather than on the streets.
Since the results were declared, Odinga has commended his supporters for "remaining calm" while Ruto has taken a conciliatory tone and promised to "work with all leaders".
Kenya's worst electoral violence occurred after the 2007 vote, when more than 1,100 people died in politically motivated clashes involving rival tribes.
If the court upholds the results, Ruto will become Kenya's fifth president since independence from Britain in 1963, taking over the reins of a country battling surging inflation, high unemployment and a crippling drought.