Dan McCready, the Democratic candidate in North Carolina’s 9th Congressional District, withdrew his concession on Thursday as new details emerged about allegations of election fraud that may have favored his Republican challenger.

McCready’s decision, first announced in an interview with Charlotte television station WSOC, comes as North Carolina is dealing with an unfolding scandal over absentee ballots. Election officials are trying to determine why many were never mailed in in certain counties that likely would have favored the Democrats in the election, and three people have told BuzzFeed News and WSOC that they were hired to collect such absentee votes, which would be a violation of state law.

Republican Mark Harris is currently leading in the election by 905 votes. McCready conceded last month about 24 hours after polls closed in the midterm elections.

“Last week we began to learn about shameful criminal activity, bankrolled by my opponent, to take away North Carolinians very rights to vote,” McCready said in a video posted Thursday on Twitter. “I didn’t serve overseas in the Marine Corps just to come back home and watch politicians and career criminals attack our democracy.”

McCready also called on Harris to “tell us exactly what he knew and when he knew it.”

I didn’t serve overseas in the Marines to come home to NC and watch a criminal, bankrolled by my opponent, take away people’s very right to vote. Today I withdraw my concession and call on Mark Harris to end his silence and tell us exactly what he knew, and when. pic.twitter.com/2hcT00DVhQ — Dan McCready for NC (@McCreadyForNC) December 6, 2018

Over the past week, the three people who have come forward to say they were hired to collect absentee ballots said they were paid by McCrae Dowless, a campaign operative who was working on behalf of Harris. Dowless has a felony record and has been convicted of perjury and financial fraud.

Voters in North Carolina have said they are confused and angry as the spotlight shines on two counties, Bladen, which has a large black population and saw 40 percent of absentee ballots not returned, and Robeson, which is 38 percent Native American and where 62 percent of absentee votes weren’t mailed in.

The entire district’s non-return rate is 24 percent, far lower than the rates in the two counties.

Harris has remained mostly silent throughout the scandal, and WSOC reporter Joe Bruno said he had been unable to reach the Republican after calls, texts and a visit to his home.

The state elections board has refused to certify the 9th District results, and the North Carolina Republican Party said it was open to a new election should it be necessary. The board can order a new vote if “irregularities or improprieties occurred to such an extent that they taint the results of the entire election and cast doubt on its fairness.”

House Minority Leader Nancy Pelosi (D-Calif.) also said earlier Thursday that Congress could refuse to seat Harris until the alleged fraud is investigated.

“The House still retains the right to decide who is seated. That is one of the powers of the House of Representatives,” Pelosi told reporters Thursday. “Any member-elect can object to the seating and swearing-in of another member-elect. We’ll see how that goes.”