“The people of North Carolina believe that our voters must have trust in our process, believe their vote must be counted, and they believe that elections must be fair,” Robert Cordle, a Democrat who chairs the elections board, said Monday. “That is why we have hearings to try to determine these things here in North Carolina.”

Mr. Cordle was the only member of the elections board to speak at length during Monday’s hearing, and the regulators appeared impassive through hours of testimony. But if four of the board’s five members ultimately conclude that “irregularities or improprieties occurred to such an extent that they taint the results of the entire election and cast doubt on its fairness,” they may order a new election.

No matter what the board decides, Monday’s revelations were an embarrassment for North Carolina Republicans, who spent years crusading against fraud — and were openly accused on Monday of underwriting misdeeds with tens of thousands of dollars in pass-through payments.

Ms. Strach’s remarks, followed by just some of the dozens of potential witnesses who were called to the North Carolina State Bar building, signaled that investigators had corroborated many of the allegations that were detailed in affidavits, interviews and news reports in recent months. Mr. Dowless, seated three rows from the back of the crowded hearing room, sat quietly and sometimes closed his eyes or bowed his head.

Mr. Dowless was called to testify near the end of Monday’s proceedings, but his lawyer said he would not address the board unless he received a form of immunity.

“I don’t think he’s going to incriminate himself because I don’t think he’s done anything wrong, but I am just telling you, it’s just not a good situation from an attorney’s standpoint to let somebody testify in a situation like that,” Cynthia Singletary, Mr. Dowless’s lawyer, said after the hearing.

Although Mr. Harris acknowledged in December that he had directed Mr. Dowless’s hiring, the Republican candidate’s allies have depicted Mr. Dowless as something of a rogue operative.