Sen. Mike Lee, R-Utah., took aim at Sen. Bob Casey over the Pennsylvania Democrat's refusal to concede the election, arguing that the Senate could refuse to seat him if he continues to rely on "illegal votes."

"If Bob Casey doesn’t concede, Pennsylvania keeps counting illegal votes, & Casey relies on those votes to claim victory, the Senate could refuse to seat him," Lee said in a post on X Saturday while citing Article I, Sec. 5, Cl. 1, which states that each "House shall be the Judge of the Elections, Returns, and Qualifications of its own Members."

The comment comes as Pennsylvania’s Senate race will be decided by a recount after Republican Sen.-elect Dave McCormick won the election by roughly 26,000 votes, or within the one percentage point margin that triggers an automatic recount under Pennsylvania law.

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Sen. Mike Lee speaks during a news conference in the Capitol on July 20, 2021. (Bill Clark/CQ-Roll Call, Inc via Getty Images)

Casey has refused to concede the election despite the contest being called by multiple outlets, instead insisting that a winner be declared after all votes are counted.

But questions remain about the votes Casey is trying to count after the Pennsylvania Supreme Court ruled that ballots that lack required signatures and dates are not allowed to be included in official results, a ruling that is being ignored by Democratic officials in Philadelphia and surrounding Bucks and Montgomery counties.

"I think we all know that precedent by a court doesn’t matter anymore in this country," Bucks County Commissioner Diane Ellis-Marseglia, a Democrat, said last week. "People violate laws anytime they want. So, for me, if I violate this law, it’s because I want a court to pay attention. There’s nothing more important than counting votes."

Sen. Bob Casey addresses supporters during a campaign rally on Sept. 21, 2018, in Philadelphia. (Mark Makela/Getty Images)

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Republican National Committee Chairman Michael Whatley has condemned Democrats in Pennsylvania, accusing the party of attempting to "steal" the election from McCormick.

"Let’s be clear about what’s happening here: Democrats in Pennsylvania are brazenly trying to break the law by attempting to count illegal ballots. They are doing this because they want to steal a senate seat," he said on X.

Lee, meanwhile, has urged Casey to abandon the fight over the ballots voluntarily and allow McCormick to take his seat in the Senate.

Republican Sen.-elect Dave McCormick and Democratic Sen. Bob Casey (Getty Images)

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"Bob Casey, you’re better than this," Lee said in another post on X. "It’s time to concede."

The Casey campaign did not immediately respond to a Fox News Digital request for comment.