The Pennsylvania Supreme Court on Monday issued a ruling reiterating its previous stance that undated or misdated mail ballots should not be counted in the 2024 election, dealing a blow to Democratic U.S. Sen. Bob Casey’s hopes that a recount and litigation will help him overcome his more than 15,000-vote deficit to Republican Dave McCormick.

The 4-3 ruling, which was requested by the Republican Party and opposed by Casey’s campaign, followed moves by elections officials in Democratic-controlled counties — including Philadelphia, Bucks, and Montgomery — to have the ballots counted despite the high court instructing them to exclude those votes earlier in the year. The ruling applies to all counties.

» READ MORE: Undated mail ballots won’t be counted in next week’s election, Pa. Supreme Court rules

Democrats in those counties and elsewhere have pushed to include mail ballots with defects related to the dates voters are required to write on them because the dates are not used by election administrators to determine whether ballots are legitimate. Instead, they only count ballots that are received between when the ballots are distributed and Election Day, making it impossible for a vote to be counted outside of that timeframe regardless of what date a voter writes on the ballot.

Republicans have argued that those votes must be excluded from the count because state law requires voters to date their mail ballots. McCormick’s campaign joined the GOP lawsuit after it was filed.

While the ruling settles how these types of ballots are handled this year, the longer legal battle may not be over because the court has not yet weighed in on the underlying question of whether rejecting undated ballots on what Democrats describe as a technicality constitutes a violation of rights guaranteed to voters by the state constitution.

In a ruling issued shortly before Election Day, the Pennsylvania Commonwealth Court found that it did, though that case centered on a special election held in Philadelphia earlier this year. The state Supreme Court stayed the lower court’s decision before Election Day, deciding at the time that it was too close to the Nov. 5 vote for any last-minute changes to rules surrounding which votes should be counted.

Democratic Justices David Wecht and Kevin Dougherty were joined by Republican Justices Kevin Brobson and Sallie Updyke Mundy in the majority decision Monday. Democratic Justices Debra Todd, Christine Donohue, and Daniel McCaffery dissented.

The total number of ballots in question is likely well under 10,000 and would not be enough to erase Casey’s deficit alone. But the three-term incumbent is also in legal fights with McCormick’s team over how various counties have handled certain categories of provisional ballots across the state.

The Associated Press has called the race for McCormick, but Casey has declined to concede.

Casey campaign manager Tiernan Donohue said Monday that the Democrat wants to ensure all legitimate votes are counted and is being opposed by McCormick’s campaign efforts to “disenfranchise” Pennsylvanians.

“Senator Casey is fighting to ensure Pennsylvanians’ voices are heard and to protect their right to participate in our democracy – just like he has done throughout his entire career,” Casey campaign manager Tiernan Donohue said. “Meanwhile, David McCormick and the national Republicans are working to throw out provisional ballots cast by eligible Pennsylvania voters and accepted by county boards.”

McCormick spokesperson Elizabeth Gregory cast the ruling as a “massive setback to Senator Casey’s attempt to count illegal ballots.”

“Bucks County and others blatantly violated the law in an effort to help Senator Casey,” Gregory said. “Senator-elect McCormick is very pleased with this ruling and looks forward to taking the Oath of Office in a few short weeks.”

Staff writer Jeremy Roebuck, Gillian McGoldrick, Katie Bernard, and Fallon Roth contributed to this article.