A new Dan Sullivan has entered the conversation surrounding the Alaska Senate race, in which incumbent Dan S. Sullivan faces a candidate with the same name.

The Republican former mayor of Anchorage, Dan A. Sullivan, endorsed GOP Sen. Dan S. Sullivan for re-election over retired teacher Dan J. Sullivan and Democratic former Rep. Mary Peltola on Tuesday.

“As the OG Dan Sullivan, I urge Alaskans to vote for Sen. Dan S. Sullivan. He’s been great for Alaska,” the former mayor wrote on Facebook.

Both Dan S. Sullivan and Peltola advanced to the general election in November after the all-party primary last week. The primary is decided by ranked-choice voting, and the top four finishers advance, regardless of political affiliation. NBC News has not yet made a call regarding who the other two candidates will be, but Dan J. Sullivan could be among them.

Alaska’s Senate race is considered one of the most competitive this cycle, when control of the upper chamber hangs in the balance. With primary votes left to count, Peltola so far has 48% of the vote, with Sen. Dan S. Sullivan taking 43%. Dan J. Sullivan — who is running as a Republican — has 2.4%, with other candidates getting considerably fewer votes.

Democrats view the election as a seat they could flip in November. The Cook Political Report rates the race a tossup.

The Sullivan saga has drawn attention as former teacher Dan J. Sullivan’s candidacy has faced legal challenges. Dan S. Sullivan and Republicans have alleged that the teacher was placed on the ballot to confuse voters and detract from the senator’s share of the vote, claiming he’s working with Peltola.

Dan J. Sullivan has denied coordinating with the Peltola campaign. Peltola has also denied any involvement with the second Sullivan campaign.

The Alaska Supreme Court ruled last month that Dan J. Sullivan can stay on the ballot after the state Division of Elections originally disqualified him. NBC News has reported that state and federal prosecutors in Alaska were investigating whether the race could be part of a conspiracy to confuse voters. A grand jury issued subpoenas this month to compel information from witnesses linked to Dan J. Sullivan’s campaign.