A North Carolina Republican has told election officials he was unaware of alleged fraud in his congressional bid.
Mark Harris said he did not realise a political consultant was allegedly collecting absentee ballots to tip the vote in his favour.
The consultant, Leslie McCrae Dowless, is accused of illegal vote manipulation.
The state board of elections has held off certifying Mr Harris as the victor in November’s vote.
The Republican claimed victory after initial results indicated he had edged out Democrat Dan McCready in the state’s ninth district by 905 votes, out of 282,717 ballots cast.
The elections board has been holding hearings this week on the case, and could order a new vote if it finds the original one was tainted.
Mr Dowless denies illegally collecting, falsely witnessing and otherwise tampering with the district’s absentee ballots.
On Thursday, Mr Harris took the stand and said he now believed a re-run of the election was warranted.
The Republican candidate said Mr Dowless had assured him his staff only helped voters obtain absentee ballots and did not do anything illegal.
Mr Harris, a Baptist pastor, recalled Mr Dowless telling him: “‘I don’t care if it’s a 95-year-old woman in a wheelchair, we do not take the ballots.'”
The Republican candidate also referred to dramatic testimony a day earlier by his son, which left both men in tears.
Mr Harris told the court his son was “a little judgmental and has a little taste of arrogance and some other things”, but that he was “very proud of him”.
On Wednesday, John Harris told the elections board he had repeatedly warned his father about the “shady” tactics of Mr Dowless.
“I thought what he was doing was illegal, and I was right,” John Harris testified, weeping, as his father also began to cry.
“I had no reason to believe that my father actually knew,” the son added.
Mr Dowless has refused to testify.
But his former workers have testified that Mr Dowless instructed them to “pre-fill” ballot request forms, get them signed by voters, then mail in the absentee ballots.
Bladen County, where Mr Dowless operated, was the only county for which Mr Harris won the mail-in absentee ballot vote.