The double Dan Sullivan drama appears to have finally come to an end.

The Alaska Supreme Court ruled on Monday that Dan J. Sullivan could appear on the ballot this year, seemingly bringing to a close a bizarre political saga hanging over the race for Senate in Alaska, a potentially consequential battleground as Democrats fight to regain control of Congress.

The court’s decision appeared to be good news for Democrats.

Republicans fear that their party’s incumbent, Senator Dan S. Sullivan, could be imperiled by the presence of Dan J. Sullivan on the ballot, arguing that voters could be confused and cast their ballot for the wrong Sullivan. They accused Democrats and former Representative Mary Peltola, who is vying to oust the incumbent senator, of being behind Dan. J Sullivan’s campaign and orchestrating an underhanded scheme to trick voters.

Ms. Peltola and state Democrats have denied the allegations, and Dan J. Sullivan, a former teacher who announced his Senate campaign in May and said he had recently registered as a Republican, insisted he was making a legitimate effort to unseat the other Sullivan.

But he was not expected to run a competitive campaign, and Republicans quickly filed complaints with Alaska’s elections division, arguing Dan J. Sullivan was not a “good faith candidate.” They pointed to several pieces of evidence: the challenger had only recently registered as a Republican; he seemed to be working with a Democratic strategist; he had a campaign website that was visually similar to the incumbent senator’s; and he appeared to have a history of donating to Democratic candidates, including Ms. Peltola.

The elections division, overseen by the state’s Republican lieutenant governor, agreed, booting him from the ballot earlier this month. But a state superior court judge reinstated him last week, saying that there was no part of the U.S. Constitution, Alaska state law or election division regulations that supported the removal.

“Despite the division’s assertion that Mr. Sullivan may be excluded from the ballot because he lacks ‘good-faith’, there is no statute which provides such a criterion,” the judge wrote.

The state Supreme Court agreed. With the deadline for election officials to print primary ballots looming on Tuesday, the court ordered the election division to include Dan J. Sullivan, and gave the division authority to determine how he “shall be listed as a candidate within the confines of existing Alaska ballot design law.” That could include an effort to differentiate the two candidates.