Alaska elections director Carol Beecher on Monday disqualified Daniel J. Sullivan Jr. from appearing on the state’s U.S. Senate primary ballot, ruling that his candidacy was filed “with a purpose to confuse or mislead and to thereby compromise the ballot’s fairness or neutrality.”

In a letter to Sullivan, Beecher wrote that the “utterly unprecedented facts” of the case led her to conclude that his declaration of candidacy for U.S. Senate “was not filed in order to declare an actual good-faith candidacy.” Beecher, a Republican whose office is overseen by Republican Lt. Gov. Nancy Dahlstrom, cited several concerns: Sullivan did not typically use the nickname “Dan”; he had recently registered as a Republican; his campaign website closely resembled that of incumbent Sen. Dan S. Sullivan; and his campaign consultant was a longtime Democratic Party supporter, including of Peltola.

“I conclude that the preponderance of the evidence is that you chose this new nickname and party affiliation because that name and party affiliation happen to be the name and party affiliation of another candidate in the race,” Beecher wrote.

The incumbent, Sen. Dan S. Sullivan, is a Republican seeking a third term. The race is seen as competitive, with former Democratic U.S. Rep. Mary Peltola expected to face him in November. Alaska uses a non-partisan primary system; the top four vote-getters in the Aug. 18 primary advance to a general election that uses ranked-choice voting.

Sullivan, a former teacher, said in a previous response to Beecher’s office that the National Republican Senatorial Committee was using “your office as a pawn to kick me off the ballot.” He told the New York Times that election officials were seeking to “protect an incumbent senator from facing competition at the ballot box” and denied coordinating with Peltola. Peltola’s campaign has also denied coordination.

“I am a qualified candidate who followed the rules and filed to run for office under my legal name,” Sullivan said in a campaign statement last week. “The people of Alaska are fully capable of deciding for themselves who should represent them in Washington. If Senator Sullivan believes he has served Alaska well during his 12 years in office, he should make that case directly to voters. He should not rely on government officials or legal maneuvers to limit who can challenge him.”

Sullivan said he has long gone by Dan, registered as a Republican after his previous political party had disbanded, and includes photos of himself on his campaign website, adding that he looks nothing like the more prominent Dan Sullivan.

The Republican National Committee quickly praised the decision. RNC Chair Joe Gruters called Sullivan “Decoy Dan” and said his removal from the ballot was a win for election integrity.

“Alaskans can rest easy that their leaders will never tolerate blatant attempts to mislead voters and rig elections like Democrats’ Decoy Dan Scam,” Gruters said in a statement. “This is the right decision that will protect Alaskans from an unprecedented attack on our democracy.”

Beecher noted that Sullivan can challenge the determination in court to try to appear on the ballot. Primary ballots are set to print on June 28.