President Trump listens as Republican Sen. Dan Sullivan of Alaska, who is running for reelection, speaks at an Oct. 13 campaign rally in Wasilla, Alaska. Alex Brandon/AP hide caption

Alex Brandon/AP

A federal judge has thrown out the Trump administration's highly unusual attempt to block the certification of results from a key U.S. Senate race in Alaska if the Republican incumbent loses.

In a ruling released Sunday, U.S. District Judge Sharon Gleason found the federal government does not have the ability to bring this lawsuit, which cited the preamble of the National Voter Registration Act.

It asked the judge to stop state officials from certifying election results to allow for an investigation into whether voters were confused by having two similarly named Senate candidates appear on Alaska's ranked-choice ballot.

But Judge Gleason concluded that such a court order would likely violate Alaskan voters' right to a secret ballot.

"The absence of any explanation from the United States as to how its requested relief could redress its alleged injury while simultaneously maintaining the secrecy of the ballot is telling," wrote Gleason, a nominee of former President Barack Obama.

The Justice Department is planning to appeal, spokesperson Kiersten Pels told NPR in a statement. "Alaskan voters deserve a fair election, not to be misled in an attempt to rig outcomes," Pels added.

Voting rights groups that stepped in to help defend Alaska against the lawsuit cheered the ruling.

"DOJ's attempt to throw out Alaska's election results before a single ballot was counted was lawless from the start, and the court saw it for exactly what it was. It was a reckless waste of taxpayer money aimed at silencing hundreds of thousands of Alaska voters," Sophia Lin Lakin, director of the American Civil Liberties Union's Voting Rights Project, said in a statement.

President Trump said he ordered this lawsuit to be filed because out of the four Senate candidates on Alaska's ballot, two have similar names — Sen. Dan Sullivan, the Republican incumbent, and Daniel Sullivan Jr., who is not affiliated with a political party.

Alaska's Republican Party supported an earlier effort in state court that tried to keep Sullivan Jr., the non-incumbent, off the ballot. But in June, the Alaska Supreme Court ruled Sullivan Jr. has the right to run as a candidate.

Still, Republican allegations of Democrats propping up Sullivan Jr. to spoil the incumbent Sullivan's chances of winning reelection have long hung over this closely watched Senate contest.

A New York Times report about Democratic campaign operatives' efforts to recruit Sullivan Jr. — which NPR has not independently confirmed — drew new attention to those allegations. Alaska's Republican Gov. Mike Dunleavy has ordered an investigation and indicated the results of the race may not be certified by the state depending on how that investigation turns out.

"If we find out there's wrongdoing, and if that means that the certification then is stopped or changed, then that's what happens," Dunleavy said during an Oct. 30 interview with NewsNation.

At an Oct. 30 press conference in Anchorage, U.S. Attorney Michael Heyman said there is an "ongoing" criminal probe by the Justice Department.

The Democratic candidate, former Rep. Mary Peltola, has denied any involvement.

In an interview Sunday with CNN's State of the Union, incumbent Sullivan said that he would accept the election results, win or lose.

This controversy hasn't stopped Alaskans from voting. Over 86,700 voters in the state have cast their ballots during early voting, according to the latest figures from Alaska's Division of Elections. And more Alaskans are expected to exercise their rights as voting continues through Tuesday's Election Day.

Additional reporting by NPR's Eric McDaniel. Edited by Benjamin Swasey