RALEIGH — The son of Republican congressional candidate Mark Harris testified Wednesday that he warned his father repeatedly that he believed a political operative now at the center of an election-fraud investigation had previously used illegal tactics to win votes.

John Harris, now an assistant U.S. attorney in Raleigh, said he advised his father in conversations and emails that he believed Leslie McCrae Dowless was “shady” and appeared to have illegally collected absentee ballots in 2016 while working for a different Republican candidate in North Carolina’s 9th Congressional District.

The younger Harris, who is 29, said he offered the advice to his father as he considered whether to hire Dowless to run his absentee-ballot program in the 2018 congressional race. He conveyed similar concerns to the campaign’s chief strategist, Andy Yates, he said. Mark Harris hired Dowless despite his son’s concerns, which he expressed starting in the spring of 2017.

At one point during his testimony, John Harris’s voice cracked and his father wept.

“I thought what he was doing was illegal, and I was right,” John Harris said about Dowless. He added: “I had no reason to believe that my father actually knew, or my mother or any other associate with the campaign had any knowledge. I think Dowless told them he wasn’t doing any of this, and they believed him.”

Harris’s dramatic testimony undercut claims by both his father, a 52-year-old evangelical minister, and Yates — who completed nearly eight hours of testimony earlier Thursday — that they had not been aware of any red flags that Dowless might be breaking the law. Investigators also shared an email between father and son in which the younger Harris wrote: “Good test is if you’re comfortable with the full process he uses being broadcast on the news.”

Months after the midterms, an election-fraud investigation in North Carolina’s 9th District is focusing on an operative who worked for the GOP candidate. (Jenny Starrs, Sarah Hashemi, Zoeann Murphy/The Washington Post)

John Harris’s account ended the third day of testimony before the North Carolina State Board of Elections, which is hearing evidence this week to decide whether a suspected ballot-tampering scheme tainted the outcome in the 9th District, where Harris leads Democrat Dan McCready by 905 votes in unofficial returns. The district runs along the South Carolina border from Charlotte to rural eastern North Carolina.

The election, the last undecided congressional race in the country, has been in limbo since November, when the board declined to certify a winner and launched an investigation instead. The board’s decision on whether to certify or call for a new election will wait at least another day, with the elder Harris scheduled to open his testimony Thursday morning.

The younger Harris told the board Wednesday that he began studying absentee-ballot tallies in the 9th District in June 2016, when his father narrowly lost the Republican primary to then-incumbent Robert Pittenger. In tiny Bladen County, Harris and Pittenger had dramatically lost the vote among mail-in voters to a third candidate, Todd Johnson — who had hired Dowless to run his absentee program.

John Harris described digging into the numbers and discovering that mailed ballots for Johnson had arrived at county election offices “in batches” — which he believed suggested that they had been collected illegally by campaign workers. It is a felony in North Carolina to collect and turn in another voter’s ballot. Harris said he told his father then of his suspicions.

Dowless, 63, a Bladen County native who declined to testify this week to avoid self-incrimination, is accused of doing just that in the 2018 cycle — hiring a team of workers to illegally collect, sign, forge and turn in ballots.

Both Yates and Harris have denied knowledge of those alleged tactics. But in another email from 2016 displayed during testimony Wednesday, the two Harrises discussed the anomalies that year — as well as the irony that Dowless had submitted a complaint to state elections officials that Democrats had employed similar tactics in Bladen County.

“Guess he didn’t like the Dems cutting into his business!” the elder Harris wrote.

In a televised interview in early January, Mark Harris told Spectrum News in Raleigh that reports, including one in The Washington Post, that he had been warned of Dowless’s alleged tactics, were untrue.

[N.C. congressional candidate sought out aide, despite warnings over tactics]

In his testimony Wednesday, the younger Harris also called into question the account of Yates, whose political consulting firm, Red Dome Group, had paid Dowless on behalf of the campaign.

John Harris said he was surprised to hear how little oversight Yates provided to ensure that Dowless was performing the services that he was being paid for. He was also surprised to hear Yates say he was shocked to learn of Dowless’s alleged tactics once the investigation began in November.

“Mr. Yates said he was shocked and disturbed by the testimony,” the younger Harris said. “I was disturbed. Less shocked.”

Harris said that after he warned Yates of Dowless, “Andy assured me, ‘Yeah, we’re going to make sure that he does what he says he’s going to do.’ ”

But in his testimony Tuesday and Wednesday, Yates describes an arrangement in which there was little oversight or accountability for Dowless’s activities. He demanded payment, for instance, for submitting far more ballot-request forms — a legal activity — than records later showed were actually submitted.

John Harris emphasized his belief that his parents did not know of Dowless’s alleged tactics, but he also acknowledged in wrenching testimony that they “wanted” to believe Dowless — perhaps against their better judgment.

The younger Harris asked the elections board if he could make a few final remarks after lawyers had completed their questioning of him.

“I love my dad, and I love my mom,” he said. “I certainly have no vendetta against them, no family scores to settle. I think that they made mistakes in this process, and they certainly did things differently than I would have done them.”

Harris also criticized both parties for working more to protect their political interests than to protect the integrity of the electoral process.