When GOP Rep. Robert Pittenger lost his primary by a narrow margin in May, he suspected something was amiss.

The congressman turned to a group of friends and family who had gathered with him on election night at a steakhouse near Charlotte and blamed the “ballot stuffers in Bladen,” according to three people at the gathering.

Pittenger’s concern stemmed from the vote tallies in rural Bladen County, where his challenger, a pastor from the Charlotte suburbs named Mark Harris, had won 437 absentee mail-in votes. Pittenger, a three-term incumbent, had received just 17.

In the days immediately after the race, aides to Pittenger told the executive director of the North Carolina Republican Party and a regional political director for the National Republican Congressional Committee that they believed fraud had occurred, according to people familiar with their discussions.