Votes cast by military personnel could assume greater importance as the race between President Trump and former vice president Joe Biden narrowed to a handful of battleground states that accept service members’ ballots after Election Day.

Authorities in Georgia, North Carolina, Nevada, Arizona, Pennsylvania and Alaska on Thursday continued to count ballots and wait for others yet to arrive, including those cast by uniformed troops and their families stationed away from their homes.

“We anticipate military ballots could play a decisive role in this election given that these ballots are some of the latest to arrive and be counted,” said Jack Noland, a researcher at the nonpartisan group Count Every Hero, an initiative of anti-corruption advocacy group RepresentUs.

Scrutiny of ballots that were not counted or received until after Election Day has intensified as Trump’s campaign mounted legal challenges in at least three states and the president has attempted to stoke doubts about the validity of continuing vote tallies.

“STOP THE COUNT!” Trump tweeted Thursday morning. In another tweet that was flagged by Twitter as potentially misleading, he also said: “ANY VOTE THAT CAME IN AFTER ELECTION DAY WILL NOT BE COUNTED!”

While Trump has also made unsubstantiated allegations in recent days of fraud and raised questions about a “mail-in ballot dump,” his campaign has said there “are and should be exceptions” for troops stationed overseas.

U.S. troops have been voting by mail since the War of 1812 and, in larger numbers, the Civil War. In 2016, troops and their families sent more than 630,000 ballots. About 20,000 of those were rejected, mostly because they arrived too late. This year, military authorities urged troops to vote early because of postal delays related to the coronavirus pandemic.

How military mail-in ballots are treated varies by state. According to research compiled by Count Every Hero, 28 states and the District of Columbia allow military ballots to be counted after Election Day. Among the states that are still counting, military ballots can be received up to 15 days after that date. Some states allow troops to vote by email or fax.

In Arizona, state rules require that military ballots must be received by Election Day. Georgia, meanwhile, permits the processing of military ballots that are postmarked by Election Day and received by Nov. 6. In Nevada, they must be postmarked by Election Day and received by Nov. 10.

Pennsylvania requires them to be signed by Nov. 2 and received by Nov. 10. North Carolina requires them to be sent by 12:01 a.m. on Election Day and received by Nov 12. Finally, Alaska allows military ballots that are postmarked by Election Day. For those coming from within the United States, the deadline is Nov. 13; for those coming from overseas that are received by Nov 18.

In a call Thursday organized by Count Every Hero, retired Gen. George Casey, who served as Army chief of staff during the George W. Bush and Obama administrations, asked state officials to include assurances when they certify state votes that all service member ballots have been counted. “We ask so much of them, they deserve to know that their voices are heard,” he said.

It was unclear Thursday how many more military ballots could arrive in battleground states, or how they could be affected by legal challenges.

Some critical states have seen larger numbers of military absentee voters this year compared with the number in 2016. In North Carolina, 14,550 service members requested absentee ballots, with 9,750 returned as of Wednesday, said Caroline Myrick, a data analyst with the state board of elections. The number of ballot requests was thousands more than for the last presidential election, she said.

Some of the thousands of remaining ballots will be tabulated as they come in, but Myrick said the number doesn’t account for service members who requested mail-in ballots but later decided to vote in person on Election Day.

In Pennsylvania around 4 p.m. Thursday, more than 340,000 mail ballots remained to be counted. The state did not provide an immediate breakdown surrounding military votes that have been received or information about those that might be still in the mail.

Officials in Georgia said on Thursday afternoon that 47,000 votes remain to be counted in that state, but that did not appear to include those that might be yet to arrive by Friday’s deadline for military ballots. According to the Atlanta Journal Constitution, an official in pivotal Fulton County, where Atlanta is located, said Thursday that all absentee-by-mail votes had been counted, leaving only provisional ballots and an “undetermined” number of military ballots.

The military does not conduct electoral polling, and it is unknown how active-duty troops will vote this year. Traditionally, military personnel have tended to skew Republican politically.

Veterans for Trump, an online coalition, has seized on the president’s allegations of impropriety and asked members to mobilize to observe ballot counting. The group did not return a request for comment, but a recorded phone message said volunteers were needed “to ensure election integrity” in Wisconsin, Michigan, North Carolina and other states with close vote margins.

The Biden campaign did not return requests for comment.