A federal judge ruled on Tuesday that a conservative group’s efforts to challenge the eligibility of hundreds of thousands of voters in the Senate runoff elections in Georgia in early 2021 did not violate the Voting Rights Act under a clause outlawing voter suppression.

In a 145-page opinion, the judge, Steve C. Jones of the United States District Court for the Northern District of Georgia, wrote that the court “maintains its prior concerns” regarding how the group, True the Vote, sought to challenge voters’ eligibility. But he said that Fair Fight, the liberal voting rights group that brought the lawsuit against True the Vote, had failed to show that the efforts were illegal.

The decision was relatively narrow, applying only to Judge Jones’s district in northern Georgia, and will do little to change the status quo: Right-wing election groups have already tried to help bring thousands of challenges to voter registrations in states across the country.

But the opinion is likely to encourage conservative activists hunting for voter fraud during the 2024 presidential election. Election officials and voting rights groups have expressed worries about these efforts, warning that an expanded campaign to challenge voters en masse could intimidate people away from the ballot box. True the Vote and similar groups, taking a cue from former President Donald J. Trump, have often spread false theories about election fraud.

“Any of these decisions that allows these kinds of mass challenges to go forward embolden that movement,” said Sophia Lin Lakin, the director of the Voting Rights Project at the A.C.L.U.

In his opinion, Judge Jones wrote that evidence from Fair Fight and individual voters in the trial did not amount to intimidation under an important section of the Voting Rights Act known as Section 11(b), which outlaws any attempt to “intimidate, threaten, or coerce, or attempt to intimidate” any voter or act of voting.

“While the court believes that actions increasing the difficulty to vote if paired with other conduct might give rise to a Section 11(b) violation in some circumstances, increased difficulty alone does not constitute voter intimidation,” Judge Jones wrote.

Voting rights experts said the ruling could raise the bar of what constitutes voter intimidation under the Voting Rights Act, and said it was yet another court decision that chipped away at the protections in the landmark law.

“He took a very narrow view of what constitutes intimidation,” Ms. Lakin said. “But raising the bar of what you need to show altogether will make demonstrating voter intimidation claims more difficult, at least in the Northern District of Georgia.”

In a footnote in the decision, Judge Jones, who was appointed to his post by President Barack Obama, was careful not to give a blessing to tactics like True the Vote’s.

“In making this conclusion, the court, in no way, is condoning TTV’s actions in facilitating a mass number of seemingly frivolous challenges,” he wrote. He added: “TTV’s list utterly lacked reliability. Indeed, it verges on recklessness.”

Fair Fight sued True the Vote three years ago, after the conservative group organized challenges in December 2020 questioning the eligibility of more than 250,000 registered Georgia voters. To spur right-wing activists to help challenge voters, True the Vote created a $1 million reward fund and offered bounties for evidence of “election malfeasance.”

Fair Fight argued in its lawsuit that finding actual fraud or ineligible voters was only a secondary concern for True the Vote, and that the real intention was to frighten Democratic-leaning voters from turning out in what were expected to be razor-thin runoff elections that would determine control of the United States Senate.

Catherine Engelbrecht, the president of True the Vote, celebrated the ruling as “an answer to the prayers of faithful patriots across America.”

“Today’s ruling sends a clear message to those who would attempt to control the course of our nation through lawfare and intimidation,” Ms. Engelbrecht wrote in a statement. “American citizens will not be silenced.”

Fair Fight, in a lengthy statement, said that federal courts were not adequately protecting Americans from ramped-up attacks on voting rights.

“While there is much to make of the court’s 145-page opinion, Fair Fight is disappointed that Georgians and voters nationwide must continue to wait for our federal courts to impose accountability in the face of widespread and mounting voter intimidation efforts,” Cianti Stewart-Reid, the executive director of Fair Fight, said in the statement.

It was unclear whether the group planned to appeal the decision.