"I am very confident that I will win this election," Ruto said in an interview at his Nairobi offices.
Poll-rigging allegations have frequently surfaced in the powerhouse of East Africa's elections, but Kenyan Deputy President William Ruto maintained he would accept the results of the vote.
"People of Kenya ultimately make their decisions. There is a wrong narrative that elections are manipulated... It is very difficult to steal an election," the 55-year-old former MP and minister said.
Ruto acknowledged that elections may at most be "influenced," but said, "We will stand (our ground) and still win against the so-called system."
Initially, the aspirational politician was going to be the nominee of the ruling party to succeed his boss, President Uhuru Kenyatta. However, Ruto has been forced to watch from the sidelines due to a surprising coalition between Kenyatta and his old foe Raila Odinga, who is now running against Ruto.
Both candidates have vowed to accept next month's result, with Odinga telling a press conference on Monday, "If we lose the elections fairly, we will accept the outcome and congratulate the winner."
Violent riots and claims of election manipulation routinely accompany recent elections. Odinga appealed the 2017 election to the Supreme Court, which, in a first for Africa, nullified the outcome and ordered a new election.
The disputed 2007 vote was marked by an eruption of politically-motivated ethnic violence, leaving more than 1,100 people dead.
Kenyatta and Ruto were indicted by the International Criminal Court for their role in the 2007-2008 killings before the cases collapsed.
For his part, Ruto said he would willingly cooperate with his rival if Odinga were to win.
"We will have... to make sure Kenya remains a democracy and Kenya moves forward," he said.