Mary Peltola's Alaska Senate campaign reportedly recruited second Dan Sullivan

The incumbent is also named Dan Sullivan.

Peltola’s campaign has denied involvement with the other Dan Sullivan, but the [New York] Times reports that her officials together with the party’s campaign arm, the Democratic Senatorial Campaign Committee (DSCC), worked to find other people named Dan Sullivan in Alaska, and encourage them to run. Their reporting is based on interviews with Peltola’s former campaign manager and other sources, together with documents and text messages related to the recruitment effort.

The incumbent is marked as the incumbent on the ballot by the word "incumbent" being placed next to their name. If there's any confusion, the voter would have been confused by any ballot they saw. They would probably have voted for Mary Peltola by accident if it was just her and the incumbent on the ballot.