A divided federal appeals court has upheld North Carolina’s deadline extension for mail-in votes to be counted in the upcoming election, calling the measure a “common sense change” at a time when the U.S. Postal Service is inundated with ballots.

In a 12-to-3 ruling, the U.S. Court of Appeals for the 4th Circuit rejected Republican efforts to block the six-day extension. The ruling allows ballots to be received up to nine days after the election as long as they are mailed on or before Nov. 3.

“North Carolina voters deserve clarity on whether they must rely on an overburdened post office to deliver their ballots within three days after Election Day. The need for clarity has become even more urgent in the last week, as in-person early voting started in North Carolina on Oct. 15,” Judge James A. Wynn Jr. wrote in the opinion published Tuesday. The majority included all three judges nominated by President Trump.

The fast-moving case is one of a series of legal battles between Democrats and Republicans over the timing and mechanics of voting amid the coronavirus pandemic and ahead of a hotly contested presidential election.

The dissenting judges warned the new deadline would “cause yet further intolerable chaos” and implored the Supreme Court to take up the case “immediately. Not tomorrow. Not the next day. Now.”

The Supreme Court on Monday allowed Pennsylvania election officials to count mailed ballots received up to three days after the election and refused a Republican request to stop the procedure.

Millions of Americans are casting ballots by mail for the first time this year because of concerns about the risks of in-person voting associated with the novel coronavirus. In North Carolina, the state board of elections voted unanimously in September to extend the deadline to receive mail-in ballots to Nov. 12 in response to concerns from the North Carolina Alliance for Retired Americans.

North Carolina is a critical battleground state, with polls showing Trump and former vice president Joe Biden running in a dead heat. Trump won North Carolina in 2016, and along with Florida, it is seen as crucial to his reelection efforts.

Republican legislative leaders tried to block the extension in state and federal court. A district judge rejected their request for an injunction because of concerns about changing voting rules so close to an election. The lawmakers, joined by national Republican committees and the president, then asked the appeals court to intervene.

In its ruling, the majority said the courts must defer to state election officials to regulate their own voting procedures. The court noted that North Carolina election officials regularly extend the state’s ballot receipt deadlines in response to hurricanes, as they did in each of the past two years.

“Recent actions of the Supreme Court make clear that it is up to a state to decide what election procedures are in effect on Election Day, and not federal courts,” Judge Diana Motz, a nominee of President Bill Clinton, wrote in a separate concurring opinion.

She called the arguments from state House Speaker Timothy K. Moore and Senate President Philip E. Berger “deeply troubling” because they challenge measures that “remove burdens on other citizens exercising their right to vote.” Lawyers for the state lawmakers and GOP officials did not respond to requests for comment.

The court said the new rules make it easier for people to vote by mail and ensure their ballots are received if there are delays “precipitated by an avalanche of mail-in ballots,” wrote Wynn, a nominee of President Barack Obama.

A Washington Post-ABC poll released Tuesday found that two-thirds of likely voters in North Carolina plan to vote early or have already cast their ballots, though just 13 percent have voted or plan to do so by mail. Interest in mail-in voting is lower in the state than in the country as a whole. The poll found 23 percent nationwide planned to vote early by mail or had already done so.

Even as it upheld the new deadline and said Republican leaders do not have legal grounds to challenge it, the court acknowledged that issues raised about the scope of the election board’s authority are far from settled.

The dissenting judges, nominated by Republican presidents, said election officials were “changing the rules in the middle of an election” and undermining the authority of elected lawmakers.

“It takes no special genius to know what this insidious formula is producing,” wrote Judge J. Harvie Wilkinson III, joined by Judges G. Steven Agee and Paul V. Niemeyer. “Our country is now plagued by a proliferation of pre-election litigation that creates confusion and turmoil and that threatens to undermine public confidence in the federal courts, state agencies, and the elections themselves.”

Scott Clement contributed to this report.