HARRISBURG, Pa. – More than 4,000 vote-by-mail applications have been challenged in 14 Pennsylvania counties, leaving election officials to decide voter eligibility during hearings that will span well over Election day.

State election officials say the “mass challenges” have focused on two separate groups — people who may have mailed in without also changing their voter registration and non-military American voters living abroad . Overseas voters are only entitled to vote under the Absentee Voting Act and Overseas Citizens for President and Congress seats.

The state had a Friday deadline of 5 p.m. for anyone to contest vote-by-mail applications; any ballots from voters whose claims have been challenged must be impounded until county election officials hold a hearing to adjudicate the claims. These hearings must take place no later than Friday, three days after Election Day.

Pennsylvania is a critical state that could be a deciding factor in the contest between the Democratic nominee Kamala Harris and Republican candidate Donald Trumpa very close race on the eve of election day. If the margin is tight, the 4,300 mail-in ballots in question could be enough to determine who wins the state and its 19 electoral votes.

The effort is pending before a federal judge deciding last week to drop a lawsuit by six Republican members of Congress seeking to compel Pennsylvania election officials to institute new checks confirming the eligibility and identity of military and overseas voters.

The first county election board hearing, held Friday in suburban Philadelphia’s Chester County, rejected all challenges to mail-in ballot applications, claims that people have moved and should have changed where they vote.

“The scary part was that they sent this letter with a voter registration cancellation form and they claimed they got 2,300 voters to cancel their voter registration” in Pennsylvania, Democratic Commissioner Josh Maxwell, Chester County, said Monday.

Challenges cost $10 per voter, and it’s not entirely clear who filed each one. In Chester County, they were filed by Diane Houser, a Trump supporter who said they were nonpartisan and from a grassroots network.

Lycoming County will conduct a hearing Friday on the 72 challenges received from Karen DiSalvo, an attorney with PA Fair Elections, a conservative group that has fueled right-wing attacks on voting procedures. DiSalvo said he made the challenges as an individual and not as a member of any organization.

“The appeals filed simply emphasize that county election officials must properly process the voter registration applications they already have for these applicants. Voters don’t need to do anything – everyone has received their ballot. To address the eligibility issues noted in the challenges, county officials should properly enroll applicants,” DiSalvo wrote in an email.

In York County, all of the challenges — 354 — were rejected Monday by the board of elections, but Chief Clerk Greg Monskie said the board agreed to keep those ballots separate during a period when an appeal can be made.

The Pennsylvania Department of State, which oversees elections, said as of Saturday there were about 3,700 challenges to mail-in ballot applications of overseas voters pending in 10 counties. There were also pending challenges in four counties to 363 voters based on alleged address changes — plus the 212 that were rejected or withdrawn in Chester County from that category.

Eric Roe, the Republican commissioner from Chester, said active duty military members, college students and people who have left Pennsylvania in search of health care are among those who have been challenged.

“It’s alarming to me that someone would take such an approach to disenfranchise legitimate voters in Pennsylvania,” Roe said. “And I can’t think of anything less American than that.”

The American Civil Liberties Union of Pennsylvania says filling out a change of address form doesn’t necessarily mean a voter has permanently moved out of state — those forms can also be used to send mail.

There are also 52 challenges under review in Lawrence County, said Tim Germani, director of voter and election services in Lawrence, and it appears that most, if not all, of them involve vote-by-mail requests from over increase. The board of elections may need to hold a hearing by Friday, he said.

In suburban Philadelphia, Bucks County, where about 1,300 appeals have been filed — most by Republican state Sen. Jarrett Coleman — officials were trying to inform voters Monday about a hearing scheduled for early Thursday. Until then, those votes will be separated during the vote count, Bucks Gov. Jim O’Malley said.

“We are doing our best to provide a notice to those voters today, and that notice will include information on how to contact the Board of Elections,” O’Malley said in a phone interview Monday.

A message was left for Coleman seeking comment.