Amid a quickly developing possible election fraud scandal in North Carolina's 9th congressional district, Democrat Dan McCready on Thursday withdrew his concession to Republican Mark Harris.

"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," McCready tweeted.

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

McCready's withdrawal of his concession comes amid mounting pressure for North Carolina to resolve the outstanding race as allegations of election fraud continue to surface.

Harris had appeared to defeat McCready by slightly more than 900 votes on Election Day last month. And for weeks following that result, it appeared Harris would serve in the new Congress. But that changed on Nov. 27th when the bipartisan state Board of Elections voted unanimously to delay certification of the election.

NBC retracted its call of the race for Harris on Thursday.

It is possible that a new election could be ordered by the state Board of Elections or the U.S. House of Representatives. The Charlotte Observer and others have called for a new election in the district.

Dallas Woodhouse, the executive director of the state Republican party, told NBC News: "We think the board of elections should hold a public hearing and fully lay out the facts. If they can show with certainty that the outcome could not have been changed, they need to certify Mr. Harris and continue to support all state and federal criminal investigations. If they can show a substantial likelihood it could have changed the race then we fully would support a new election."

At the center of the controversy are claims that absentee ballots were improperly interfered with, according to witnesses and records. Investigators are digging into those allegations.