Independent candidate Wangui Ngirici has threatened to move to court to challenge Kirinyaga Governor Anne Waiguru's victory in last week’s elections.
She claimed the governor polls were rigged in favour of Ms Waiguru and vowed to file a petition in the High Court.
Ms Ngirici said she has enough evidence that there was massive rigging.
"My 51,000 votes were stolen and that is how I lost," she told a congregation at St Thomas Kerugoya Anglican Cathedral on Sunday.
Ms Ngirici said she will fight until she gets justice.
"I'm a happy woman because God is revealing to me what happened during the polls," she said.
She appealed to her supporters to remain calm as she prepares to seek legal redress.
Ms Waiguru recaptured her seat in hotly contested elections on August 9.
She was declared winner by county elections manager Jane Gitonga at the Kerugoya Catholic Hall under tight security.
Ms Waiguru, who defended her seat under the United Democratic Alliance (UDA), garnered 113,088 votes against her closest rival Ms Ngirici's 105,677.
The tallying of the governor’s polls was marred by violence. As the results were announced, General Service Unit (GSU) officers were on guard in and outside the hall.
Tension mounted as heavily armed officers patrolled the area surrounding the county tallying centre and Kerugoya town streets.
But Ms Ngirici was conspicuously absent during the release of the results.
Immediately after Ms Waiguru was declared winner, she said she will focus on her development agenda.
She thanked residents for voting for her.
"I'm excited following the resounding victory. I owe my win to the residents who voted for me overwhelmingly," she said.
She dismissed Ms Ngirici’s claims that the polls were rigged in her favour.
She said Ms Ngirici has the right to challenge her victory in court instead of engaging in lawlessness.
"My opponent has an opportunity to file a petition and the court will determine who really won," she said.
Ms Waiguru said it was primitive for anyone to cause chaos for losing in an election.
"The violence which was witnessed in this region is unacceptable," she said.
After the polls, Ms Ngirici’s supporters rioted in various parts of the region.
At the Kirinyaga Central constituency tallying hall, poll materials and computers belonging to the Independent Electoral and Boundaries Commission (IEBC) were destroyed during the demonstrations.
Police intervened and ended the rioting.
Ms Waiguru said she garnered the majority of votes in Gichugu constituency, her home turf, to win the polls.
"You know, charity begins at home," said Ms Waiguru, who was accompanied by her husband Kamotho Waiganjo.