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HARRISBURG, Pa. (AP) — More than 4,000 mail ballot applications have been challenged across 14 Pennsylvania counties, leaving election officials to decide voter eligibility during hearings that will extend well past Election Day.

State elections officials say the “mass challenges” focused on two separate groups -- people who may have forwarded their mail without also changing their voter registration and nonmilitary U.S. voters living overseas. The overseas voters are only entitled to cast ballots under the Uniformed and Overseas Citizens Absentee Voting Act for president and congressional seats.

The state had a 5 p.m. Friday deadline to for anyone to challenge mail-in ballot applications; any ballots from those voters whose applications were challenged must be sequestered until the county elections board officials hold a hearing to adjudicate the claims. Those hearings must be no later than Friday, three days after Election Day.

Pennsylvania is a critical swing state that could be a deciding factor in the contest between Democratic nominee Kamala Harris and Republican nominee Donald Trump, a very close race on the eve of Election Day. If the margin is tight, the 4,300 mail ballots at issue could be enough to determine who wins the state and its 19 electoral votes.

The effort follows a federal judge’s ruling last week to throw out a lawsuit by six Republican members of Congress seeking to make Pennsylvania election officials institute new checks confirming military and overseas voters’ eligibility and identity.

The first county elections board hearing, conducted Friday in suburban Philadelphia’s Chester County, resulted in rejection of all of the challenges made to mail ballot applications, claims that people have moved and should have changed where they vote.

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

The challenges cost $10 a voter and it’s not entirely clear who filed each of them. 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 it received from Karen DiSalvo, a lawyer with PA Fair Elections, a conservative group that has fueled right-wing attacks on voting procedures. DiSalvo said she made the challenges in her capacity as an individual and not as a member of any organization.

“The challenges submitted simply point out that the county election officials must properly process the voter registration applications that they already have for these applicants. The voters do not need to do anything –- all have received their ballot. To resolve the eligibility issues noted in the challenges, county officials should properly register the applicants,” DiSalvo wrote in an email.

In York County, all the challenges — 354 — were denied Monday by the elections board, but chief clerk Greg Monskie said the board agreed to keep those ballots segregated during a period in which an appeal can be made.

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

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Eric Roe, Chester’s Republican commissioner, said people who had been challenged included active-duty military members, college students and people who left Pennsylvania seeking medical care.

“That is alarming to me that someone take up such an approach to disenfranchise legitimate Pennsylvania voters,” 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 does not necessarily mean a voter has moved out of the state permanently — those forms can also be used to get mail forwarded.

There are also 52 challenges being reviewed in Lawrence County, said Tim Germani, director of voter and elections services in Lawrence, and it appears most if not all relate to overseas mail ballot requests. The elections board may need to conduct a hearing by Friday, he said.

In suburban Philadelphia’s Bucks County, where about 1,300 challenges were filed — most of them by Republican state Sen. Jarrett Coleman — officials were trying to notify voters Monday about a hearing scheduled for early Thursday. Until then, those votes will be segregated during the vote counting, said Bucks governmental spokesman Jim O’Malley.

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

A message seeking comment was left for Coleman.