North Carolina's elections board Thursday ordered a new election in the nation's last undecided congressional race after the Republican candidate conceded his lead was tainted by evidence of ballot-tampering by political operatives working for him.

The State Board of Elections voted 5-0 in favor of a do-over in the mostly rural 9th Congressional District but did not immediately set a date.

In moving to order a new election, board chairman Bob Cordle cited "the corruption, the absolute mess with the absentee ballots."

"Today was a great step forward for democracy in North Carolina," the Democrat in the race, Dan McCready, tweeted afterward. He said the voters deserved justice "from the moment the first voice was silenced by election fraud."

The vote came after GOP candidate Mark Harris, in a surprising turn, dropped his bid to be declared the winner and instead called for a new election. He reversed course on the fourth day of an election board hearing at which investigators and witnesses detailed evidence of ballot fraud by operatives on his payroll.

"Through the testimony I've listened to over the past three days, I believe a new election should be called," Harris said. "It's become clear to me that the public's confidence in the 9th District seat general election has been undermined to an extent that a new election is warranted."

At the same time, Harris denied any knowledge of the illegal practices allegedly used by his operatives.

Harris left the hearing room without answering questions. It was not immediately clear whether he intends to run in a new election.

The decision Thursday could leave the seat empty for months. The elections board's attorney plans to review the laws on scheduling new primaries and a new general election and propose dates to the elections board for its approval.

Harris led McCready by 905 votes out of about 280,000 cast last fall in a district that includes part of Charlotte and extends eastward through several counties along the southern edge of the state. But the state refused to certify the outcome as allegations surfaced that Harris political operative Leslie McCrae Dowless may have tampered with mail-in absentee ballots.

According to testimony and other findings detailed at the board hearing, Dowless conducted an illegal "ballot harvesting" operation while working for Harris. Dowless and his assistants helped voters obtain absentee ballots and then gathered up the filled-in ballots from them by offering to put them in the mail, the board was told.

Dowless' workers in rural Bladen County testified that they were directed to collect blank or incomplete ballots from voters, forge signatures on them and even fill in votes for local candidates. It is generally against the law in North Carolina for anyone other than the voter or a family member to handle someone's completed ballot.

Harris told the board that he is still dealing from health problems caused by a blood infection that landed him in a hospital and led to two strokes since the election, adding, "I struggled this morning with both recall and confusion."

But he insisted: "Neither I nor any of the leadership of my campaign were aware of or condoned the improper activities that have been testified to in this hearing."

Harris also testified that Dowless had assured him that he wouldn't collect absentee ballots in violation of state law. "I'll never forget. He said it again and again. He said, 'We do not take the ballot,'" the candidate testified.

No criminal charges have been filed so far in the case.

The congressional seat has been in Republican hands since 1963.

The board is made up of three Democrats and two Republicans.