Washington (CNN) The campaign of North Carolina Republican Mark Harris still owed more than $53,000 after last month's election to a consulting firm at the center of an absentee ballot effort that has sparked allegations of fraud and could trigger a new House election, new filings show.

More than $34,000 of Harris' debt to Red Dome Group centered on a "reimbursement payment for Bladen absentee" work and other election efforts, according to a post-election report Harris' campaign filed late Thursday with the Federal Election Commission.

Red Dome hired Leslie McCrae Dowless, a veteran political operative, to work on the get-out-the-vote operation on Harris' behalf. Dowless, who pleaded guilty to federal insurance fraud in 1992, is now at the center of state and local investigations probing whether absentee ballots were used to alter the results in Bladen County, where Harris won 96% of the absentee vote.

Dowless has denied any wrongdoing in comments to The Charlotte Observer. He has not responded to CNN requests for comment.

The allegations of ballot tampering now have cast doubts on Harris' 905-vote advantage over Democrat Dan McCready in North Carolina's 9th Congressional District -- the last unresolved race in this year's tumultuous midterm elections.

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