JUNEAU, Alaska (AP) — A federal judge on Sunday dismissed a Justice Department lawsuit seeking to block certification of Alaska’s U.S. Senate race if Republican incumbent Dan Sullivan loses, the latest development in a ballot controversy that has roiled the final days of one the nation’s most closely watched races.

Sullivan, an ally of President Donald Trump, faces Democrat Mary Peltola, a former congresswoman, in a race that is among a handful expected to determine which party controls the Senate for the final two year's of Trump's term.

Tuesday’s ranked-choice election also includes two candidates who have done little campaigning, one of whom shares the incumbent’s name. It was that candidate's presence on the ballot that prompted Trump to push for the lawsuit out of fear he would siphon votes from the incumbent.

Shortly after the ruling, the Justice Department filed a notice saying it was appealing: “Alaskan voters deserve a fair election, not to be misled in an attempt to rig outcomes,” a department spokesperson said in a statement.

The lawsuit, filed less than two weeks before the election and as early voting was underway, called for an investigation into whether votes for retired teacher Dan J. Sullivan were intended for the senator. The state said the case lacked merit and argued there would be no way to determine that without violating voter privacy.

U.S. District Court Judge Sharon Gleason wrote in the order that the relief the federal government seeks is “infeasible” because many voters have already cast their ballots.

“More fundamentally, the United States provides no workable plan as to how it proposes to segregate ballots cast for Daniel J. Sullivan on Election Day and then conduct a court-ordered unspecified 'investigation' of those ballots in a manner that would preserve voter secrecy,” she wrote.

Peltola’s campaign and the Democratic Senatorial Campaign Committee argued that the case lacked any legal basis and amounted to election interference.

“Today’s ruling is a victory for democracy and a clear message to Donald Trump and Senate Republicans: No one, no matter how powerful, can toss out free and fair elections just because they don’t like the result," said the committee's executive director, Devan Barber.

The Justice Department, attorneys for the state and Peltola’s campaign did not immediately return messages seeking comment.

Senator says he expects ‘to lose a lot of votes’ to the other Dan Sullivan

The senator and his allies, including Trump, for months have portrayed Dan J. Sullivan as a sham candidate intent on confusing voters and helping Peltola.

Earlier Sunday, Sen. Sullivan told CNN that he thought the presence of the second Sullivan on the ballot would affect the election.

“I’m sure I’m going to lose a lot of votes to that trickery,” he said.

He also said he doubted claims by Peltola that she had no idea her top political aides were involved in recruiting Dan J. Sullivan to run as a way to confuse voters.

“There is no way this went on for a year that they weren’t informing her,” Sullivan told CNN’s “State of the Union.” “She got caught lying, and she’s still lying to the Alaskan people, the media, to all of us.”

The senator's campaign did not immediately respond to a request for comment on the Sunday court ruling.

In the week before Election Day, The New York Times reported that Peltola’s campaign was involved in efforts to recruit the second Sullivan. Shortly after entering the race in June, Dan J. Sullivan said he’d had no contact with her campaign about running. He has not responded to multiple messages over the past few days.

His recent public absence prompted a social media post Sunday by the president: “The Fake Daniel J. Sullivan, Jr., has DISAPPEARED! Nobody can find him, including Law Enforcement.”

Peltola’s campaign responded to the Times story by saying it had no involvement in the campaigns for either Sullivan: "I am not interested in tricking voters,” Peltola said during a recent campaign event.

In its statement indicating its plans to appeal, the Justice Department said the federal judge dismissed the case on procedural grounds but did not dispute the government's argument that Dan J. Sullivan entered the race “as a frivolous candidate to confuse voters.”

Multiple investigations look into whether Dan J. Sullivan was recruited as a decoy candidate

State courts, including the Alaska Supreme Court, rejected an earlier Republican-backed effort to block the retired teacher from the August open primary ballot on which he appeared as Daniel J. Sullivan Jr., with no party affiliation. The senator was listed as Dan S. Sullivan, Republican and incumbent.

Both Sullivans appear the same way on the general election ballot. Peltola placed first in the primary, followed by the senator. Dan J. Sullivan received about 2.5% of the primary vote, but that was enough to finish within the top four and qualify for the Nov. 3 ranked-choice election.

Attorneys for the Alaska Department of Law represented state elections officials in the case and asked Gleason, who was appointed by former Democratic President Barack Obama, to toss the lawsuit. They filed a scathing response to the federal government’s complaint, calling it “meritless.”

Alaska also said the state had taken “significant steps” to distinguish the two Sullivans on the ballot. Voters who still might be confused could ask for help or look up candidate biographies and other information in state-distributed election pamphlets.

Republicans, including ones working with Trump, also have a long history of backing decoy candidates in elections. The governor, a Republican, has ordered an investigation and suggested he may not certify a possible Peltola victory.

In her ruling, Gleason wrote that the Trump administration’s attempt to block certification ran counter to the Constitution, which gives states the authority to run elections. She also cited the Supreme Court’s Purcell principle, which holds that federal courts should generally not change election rules too close to an election.

Kristen Clarke, general counsel of the NAACP, which had filed a brief supporting the case’s dismissal, called the judge’s decision “a big win for the voters in Alaska.”

“The law is clear, and the DOJ’s case was a baseless, eleventh hour attempt to hijack this midterm election,” she said.

On Thursday, the Justice Department escalated a criminal investigation over the presence of Dan J. Sullivan on the Alaska ballot, issuing a raft of new grand jury subpoenas, a person familiar with the matter told The Associated Press. The FBI also has begun contacting people who donated to him, some of whom told the AP that the agents were asking if they had been misled about which candidate they were supporting.

___

Riccardi reported from Washington. Associated Press photographer Lindsey Wasson in Anchorage, Alaska, and AP writer Ali Swenson in Washington contributed to this report.