A senior member of Kenya's electoral commission (IEBC) has resigned, saying the country is unable to hold credible elections next week.
Roselyn Akombe said the IEBC was under political "siege", unable to reach consensus or take any decisions.
Now in the US, she told the BBC she had feared for her safety while in Kenya after receiving numerous threats.
Last week, opposition leader Raila Odinga pulled out of the 26 October presidential re-run.
The Supreme Court annulled the result of the original 8 August poll, which saw current President Uhuru Kenyatta declared winner, after finding irregularities and illegalities.
In a BBC Newsday interview from New York, Ms Akombe said the election commission's IT head, Chris Msando, was "brutally murdered" before the August poll, and "you'll be suicidal to think that nothing will happen to you".
"I have never felt the kind of fear that I felt in my own country," Ms Akombe told the BBC.
President Kenyatta is seeking a second term on his birthday
Does she think the election can go ahead?
In a statement, Ms Akombe said she had "agonised over the decision to leave the IEBC (Independent Electoral and Boundaries Commission).
"I have tried the best I could do given the circumstances. Sometimes, you walk away, especially when potentially lives are at stake. The commission has become a party to the current crisis. The commission is under siege.
"The commission in its current state can surely not guarantee a credible election on 26 October 2017."
And in the BBC interview, she said: "Would it be a credible election? Absolutely not.
"There is a very high likelihood that the mistakes that some of the presiding officers made during the last election will be repeated."
She said IEBC members had been voting along partisan lines, without discussing different issues on merit.
Commissioners and other IEBC personnel were facing intimidation by political actors and protesters, Ms Akombe said.
She added that the death threats were anonymous threats, and she had been put under pressure to resign.
She said she did not "feel safe enough to be able to go home" in the foreseeable future.
Where does this leave the commission's reputation?
Dickens Olewe, BBC Kenya analyst
It is a big blow for the beleaguered commission, whose credibility had already taken a big hit after the Supreme Court annulled the 8 August election.
The commission was already reeling from last week's surprise withdrawal of Mr Odinga from the election re-run.
Ms Akombe's revelation that the commission is beset by internal wrangles and is pliable to partisan interests dispels any illusion that it is an independent body.
She also questioned the commission's leadership, saying the chairman Wafula Chebukati was ineffectual.
Mr Chebukati has appealed to parties not to interfere
Her assessment of Mr Chebukati lays credence to media reports that he has been undermined by other commissioners as he tries to implement changes before the repeat election.
It is hard to imagine the commission will recover from these shocking revelations to organise a free, fair and credible election.
When the commission settled on 26 October as the date for the repeat election, President Uhuru Kenyatta's supporters were quick to point out that it was also his birthday.
It seems right now that the only thing that is certain is that Mr Kenyatta will turn 56.
What do the IEBC and Mr Kenyatta say?
The IEBC said it regretted Ms Akombe's decision to quit.
At a press conference, Mr Chebukati conceded that it was "difficult" to guarantee the election, and he urged political parties not to interfere in the process.
Mr Kenyatta has not yet commented on Ms Akombe's resignation, but he called on the nation to spend the weekend in an "extended period of prayer and reconciliation".
He has been criss-crossing the country as part of his election campaign, insisting that the poll will go ahead.
The IEBC has said that Mr Odinga's name will remain on the ballot paper, arguing that he has not filled in a legally required form to inform it of his decision to pull out.
Mr Odinga insists that he does not need to fill in the form, and has organised mass protests to demand electoral reforms before a re-run is held.
The IEBC also says that the names of five minor candidates - who obtained about 1% of the vote between them in the August poll - would appear on the ballot paper. A sixth minor candidate has been declared bankrupt since the August poll, disqualifying him from running again.
The electoral commission said Mr Kenyatta had won the August vote by a margin of 1.4 million votes - or 54% of the total, compared to Mr Odinga's 45%.
Could there be unrest?
Rights groups say about 70 people have been killed in protests since the August poll, and police were "directly implicated" in 33 of the deaths in the capital, Nairobi.
The violence is nowhere near that seen in Kenya after disputed polls in 2007, when at least 1,200 people were killed.
In parts of western Kenya which back Mr Odinga, election officials have been intimidated, raising fears of more trouble on election day.