Three Republican-led counties in Pennsylvania — Berks, Fayette and Lancaster — have refused to count all valid votes from the May 17 primary election for Senate, Congress, governor and the state legislature for weeks over opposition to the state's rules regarding undated mail-in ballots.

Officials in all three counties informed the state last month that they would not count mail-in votes that had not been properly dated, according to the Associated Press.

Pennsylvania mail ballots instruct voters to write a date next to their signature on the outside of mail-in return envelopes, although these dates do not determine whether voters are eligible or if votes were cast on time. A federal appeals court ruled in May that undated mail-in ballots must be counted, ruling that the dates are "immaterial." The U.S. Supreme Court, even with three Trump-appointed justices, allowed the ruling to stand last month. A state court similarly ruled in the Republican Senate primary that undated ballots should be counted.

The Pennsylvania Department of State earlier this month sued the three counties, asking a state court to order them to include all valid ballots "even if the voter failed to write a date on the declaration printed on the ballot's return envelope."

The department said in the lawsuit that the handwritten date "is not necessary for any purpose, does not remedy any mischief and does not advance any other objective," and that "allowing just three county boards to exclude votes that all other county boards have included in their returns creates impermissible discrepancies in the administration of Pennsylvania's 2022 primary election."

"Interpreting Pennsylvania law to allow a county board of election to exclude a ballot from its final certified results because of a minor and meaningless irregularity, such as a voter omitting a date from the declaration on a timely received ballot, would fail to fulfill the purpose of the Pennsylvania Election Code and would risk a conflict with both the Pennsylvania Constitution and federal law," the lawsuit said.

"It is imperative that every legal vote cast by a qualified voter is counted," Molly Stieber, a spokeswoman for state Attorney General Josh Shapiro, told the New York Times. "The 64 other counties in Pennsylvania have complied and accurately certified their election results. Counties cannot abuse their responsibility for running elections as an excuse to unlawfully disenfranchise voters."

Berks County Commissioner Christian Leinbach said during an appearance in court on Thursday that he does not have "discretion to determine whether a date is material or immaterial."

"I simply am obligated to look at the clear language of the law that says undated and/or unsigned ballots will not be counted," he said during a hearing, claiming that rulings on the ballots have been "anything but clear."

Leinbach said he "could not in good conscience vote to certify undated ballots," adding that "this type of issue is what is causing a lack of trust in the system."

Lancaster County officials told the Philadelphia Inquirer the county had "properly certified" its results in accordance with state law and court orders.

"The Commonwealth's demand is contrary to the law or any existing court order," the county said. "The County will vigorously defend its position to follow the law to ensure the integrity of elections in Lancaster County."

Fayette County officials argued in a court filing that the state did not have the authority to force it to count the undated ballots, according to the AP, adding that the state had missed a deadline to appeal a county board decision. The county also cited ongoing litigation before the Supreme Court, which has yet to rule on the merits of the appellate court ruling.

It's unclear which way the Supreme Court may rule. Only Justices Samuel Alito, Clarence Thomas and Neil Gorsuch dissented in the earlier emergency order, arguing that the lower court ruling was "very likely wrong."

The American Civil Liberties Union defended the appellate court ruling after Alito's dissent.

"Every vote matters, and every valid vote should be counted. Voters may not be disenfranchised for a minor paperwork error like this one," ACLU attorney Ari Savitzky said in a statement. "The Third Circuit was correct in unanimously reaching that conclusion. We are thrilled for these voters that their ballots can finally now be counted, consistent with the requirements of federal law."

The dates on the absentee ballot envelopes neither help determine whether a voter is eligible nor whether the ballot was cast by the deadline, Matthew Weil, the director of the Elections Project at the Bipartisan Policy Center, said in a statement.

"Exploiting inconsequential errors or omissions to invalidate otherwise eligible ballots received by the deadline is poor policy and bad for democracy," he said. "The fact that the state already accepts ballots with incorrect or invalid dates only demonstrates how inconsequential this requirement is to determine the voter's and the ballot's eligibility."

Democratic election lawyer Marc Elias warned that the situation in Pennsylvania is "far more disturbing than those we have seen elsewhere."

The three counties have a combined population of over 1 million people, he noted, and the issue causing the counties to contest the results has "been fully litigated in both federal and state courts."

"Most importantly, these counties did not refuse to submit any election results at all. Worse, they submitted results that intentionally exclude lawful votes," he said, adding that "this is how Republicans are planning to steal elections in the future."

Nonpartisan election law experts agreed that the trend could cause chaos on a larger scale.

"Had this unfolded on this kind of timeline in 2020, it really could have created problems, because there would have been questions about whether the state could have actually named a slate of electors," Robert Yablon, a law professor at the University of Wisconsin Law School, told the Times. "You could imagine there being disputed slates of electors that were sent to Congress, and it could have been a big mess."