Dave McCormick once fought to have undated mail ballots counted. Now, in tight race with Bob Casey, he’s suing to block them.

As vote counting continues this week in Pennsylvania’s tight Senate race, attention is once again shifting toward the largest and most hotly contested tranche of remaining votes that could help Democratic Sen. Bob Casey make up his deficit.

At least four counties — including Philadelphia, Bucks, Montgomery, and Centre — have voted to include thousands of undated and misdated mail ballots in their final vote tallies in apparent defiance of earlier rulings from the Pennsylvania Supreme Court.

That move prompted a pair of new lawsuits Thursday from Republican candidate Dave McCormick and his GOP allies seeking to block them — and, in McCormick’s case, a reversal from his position in 2022, when he pushed courts to order the inclusion of undated ballots amid another tight contest, his GOP primary race that year against TV doctor Mehmet Oz.

Heading into last week’s election, the matter appeared to be settled. The state’s Supreme Court justices had twice ruled that for the 2024 election counties should reject mail ballots submitted by voters who’d failed to write the correct date on their ballot envelope, as required by state law.

Now, the rebellious votes by some counties and the ongoing fight between Casey and McCormick — who was declared the winner last week by the Associated Press and currently leads his rival by just over 25,000 votes — threatens to rip open the debate once again.

“Various county boards are seeking to alter the rules of the election at the thirteenth hour,” lawyers for the Republican National Committee and the Pennsylvania GOP wrote in a filing Thursday asking the Pennsylvania Supreme Court to reiterate its stance that undated ballots should be rejected this year.

“By counting undated and misdated ballots for the 2024 General Election, they are disobeying this court’s commands many times over,” the attorneys continued. “At best, they are confused; at worst, they are openly defying the authority of this court.”

Though the votes by Philadelphia, Bucks, Montgomery and Centre Counties will almost certainly be overturned in court, they continue a recent pattern by majority commissioners in all four to vote for the inclusion of undated ballots.

None of the commissioners who supported their inclusion couched their votes in terms of the ongoing Senate race.

Instead, they argue the dates serve no meaningful purpose as elections officials don’t use them to determine whether a ballot was received on time. Rejecting them, they say, unfairly disenfranchises thousands of otherwise eligible voters each year. Some have also pointed to a recent ruling by the state Commonwealth Court that found that the decision to exclude undated ballots in a special election in Philadelphia earlier this year amounted to a violation of rights guaranteed to voters by the state’s constitution.

But for Casey, those votes could prove particularly important in his longshot bid to hang on to the Senate seat he’s held since 2007.

Though McCormick is attending orientation for new senators this week, Casey has yet to concede and has said he has no plans to do so until all legally cast ballots are counted. With the margin dividing the candidates currently hovering below 0.5%, the Department of State declared a statewide recount on Wednesday.

» READ MORE: Pennsylvania’s Senate race between Dave McCormick and Bob Casey is going to a recount. How will it work?

Because Democrats are overwhelmingly more likely to vote by mail than Republicans, Casey is likely to benefit most from the inclusion of mail ballots that would have been rejected for missing or incorrect dates.

That’s doubly true in many of the counties that have voted to include them this year — especially Philadelphia — where Casey has outperformed McCormick in the overall vote.

It’s unclear just how many undated or misdated ballots were submitted by voters across the state in this election. The Department of State estimated earlier this week that there were roughly 20,000 mail ballots left to be counted statewide as county boards of elections met to decide various challenges to the votes.

As Bucks County’s Board of Elections met earlier this week to decide the fate of roughly 400 undated or incorrectly dated ballots in their county, commissioners ignored advice from the county’s solicitor to reject them in compliance with the recent rulings from the Pennsylvania Supreme Court.

“I just can’t vote to reject them,” said Commissioner Diane M. Ellis-Marseglia, citing her hesitancy to needlessly disenfranchise any county voter. “I just can’t.”

She and board chairman Bob Harvie voted for their inclusion.

McCormick’s campaign appealed that decision, suing the board in Bucks County Common Pleas Court Wednesday night.

“The Pennsylvania Supreme Court has clearly prohibited this action,” his attorneys Walter Zimolong and Joseph A. Cullen wrote.

McCormick had previously fought to have undated ballots counted during his similarly tight 2022 GOP primary race against Oz.

“The … only basis for disenfranchising these voters is a technical error that is immaterial under both state and federal law,” his attorneys wrote in legal filings at the time.

Casey’s campaign was quick to pounce Thursday on what they cast as McCormick’s blatant reversal, calling it “hypocritical” and “further proof of his determination to disenfranchise Pennsylvania voters.”

As of Thursday afternoon, hearings had not been scheduled in either of the GOP challenges before the Pennsylvania Supreme Court or Bucks County’s Court of Common Pleas.

But McCormick’s campaign insisted that no matter how those court battles to come and the ongoing recount played out, they remained confident he would still emerge the race’s victor.

“There is one impossible truth to all of this,” said Mark Harris, the campaign’s lead strategist. “When counting is done, Dave will be winning by tens of thousands of votes. It will not be close.”

Staff writer Fallon Roth contributed to this article.