“What has been challenging about this case and this investigation is that, as has been widely reported, certain activity has gone on for years,” the prosecutor, Lorrin Freeman, said last week. “The more interviews you do, the more interviews you have to do.”

Ms. Freeman, who is the Wake County district attorney and began investigating Mr. Dowless’s activities in Bladen County after the local prosecutor recused himself, said on Wednesday that Mr. Dowless had been arrested in the morning and was taken to Raleigh for processing. Mr. Dowless’s secured bond was set at $30,000, and he was ordered to avoid contact with anyone who was identified in the indictments.

Four other people were also indicted and face charges of conspiracy to obstruct justice and of illegally possessing absentee ballots. One of the four was also accused of falsely signing the voter certification on an absentee ballot.

Prosecutors could eventually seek additional charges against Mr. Dowless or his associates, especially in connection with the 2018 general election. The federal authorities have not said whether they are investigating Mr. Dowless.

Mr. Dowless has some familiarity with the criminal justice system, and his record includes felony convictions for perjury and fraud. But his background did not keep him from working for Mr. Harris, as well as other Democratic and Republican politicians who were seeking office in southeastern North Carolina.

[Read: Inside a Fly-by-Night Operation to Harvest Ballots in North Carolina]

There, Mr. Dowless built a reputation as a savvy organizer of effective absentee ballot efforts that, at least sometimes, seemed to rely on criminal conduct and a network of workers with little legal knowledge but a need for quick cash. In 2017, just months after Mr. Dowless worked for one of Mr. Harris’s rivals during a campaign for Congress, Mr. Harris hired him for his 2018 House bid. In doing so, Mr. Harris ignored the misgivings of one of his sons, who memorialized his concerns in an email that became public last week.

“The key thing that I am fairly certain they do that is illegal is that they collected the completed absentee ballots and mail them all at once,” John Harris wrote to his father in 2017.