Del. Nicholas J. Freitas (R-Culpeper) during his unsuccessful run for the GOP nomination for U.S. Senate in 2018. (Steve Helber/AP)

Del. Nicholas J. Freitas (R-Culpeper) said Friday that he will mount a write-in campaign for reelection this fall after a paperwork mix-up prevented him from qualifying for the ballot.

Freitas, who was elected to his seat in 2015, failed to file paperwork in time to qualify as the Republican nominee. This week, the Virginia State Board of Elections denied his appeal to get onto the ballot.

The slip-up is a gift for Democrats in a year when all 140 seats in the General Assembly are up for election in November and the balance of power in the legislature is at stake. Republicans are nursing a 20-to-19 majority in the Senate and a 51-to-48 edge in the House of Delegates, with one vacancy in each chamber.

Freitas, a former Green Beret, represents a rural district in Culpeper, Orange and Madison counties that has been reliably Republican. Now, Democrat Ann Ridgeway, a former teacher and juvenile probation officer, will be the only candidate on the ballot for the 30th District.

The Freitas campaign said early Friday that he will mount an extensive effort to publicize his candidacy and to encourage supporters to vote and write his name on the ballot.

“Being the Republican nominee for the 30th District is not a responsibility that I take lightly, and so I am committed to running to hold this seat for the Republican Party,” Freitas said in a statement. “The conservative majority in the 30th deserves an advocate fighting for them in the General Assembly and does not deserve to be disenfranchised by Richmond bureaucrats.”

Freitas has accused the elections board of unfairly targeting a Republican district and being influenced by Democratic Gov. Ralph Northam. The board and the state department of elections said Freitas simply did not follow the rules.

Two other candidates for the House — one Republican and one Democrat — also had deadline problems were allowed onto ballots because their circumstances were different from Freitas’s.

Freitas also said he will not seek any financial help from the House Republican caucus to stage the write-in effort.

“I am committed that my campaign to retain this seat will not impede the effort to elect other Republicans across Virginia,” he said.

The situation has led to tension within the party. A former aide to Freitas engaged in a spat on Facebook with House Majority Leader Todd Gilbert (R-Shenandoah), accusing GOP leaders of not supporting Freitas. Gilbert shot back: “Oh YOU must be the mastermind behind the scenes who would rather run a write-in campaign than try to get a Republican on the ballot in an otherwise safe district when control of the state government is at stake. Shame on me?”

Last year, Freitas ran unsuccessfully for his party’s nomination to challenge U.S. Sen. Tim Kaine (D-Va.), who easily won reelection against GOP nominee Corey A. Stewart.