Former U.S. Attorney Pat Meehan (R) is now facing a court challenge to his nominating petitions.

Four Pennsylvania Republicans are trying to have Meehan's name removed from the 7th district primary ballot because of an "outright pattern of impropriety in the signatures, addresses, and dates" of his 3,623 signers. For that to happen, the court would have to find that more than 2,600 of the signatures are invalid.

Last week, Meehan -- a top GOP prospect – identifted four signatures that had potential problems. As result, the campaign referred the matter to the Delaware County prosecutor.

A spokesman for state Rep. Bryan Lentz, the expected Democratic nominee, called Meehan's petition a "forgery."

"This challenge will demonstrate that the instances of forgery and fraud in Meehan's petitions extend far beyond what Meehan and his organization was willing to admit in their confession to the district attorney last week," Lentz campaign manager Vincent Rongione said in a statement. "Given the pervasive fraud and systemic abuse of the public trust Pat Meehan may not have met the legal standard necessary to placed on the ballot."

Lentz and Meehan are running for Rep. Joe Sestak's (D-Pa.) open seat.

In a letter to Lentz that was released to reporters, Meehan called the challenge a "shameless stunt." The Meehan camp has charged that 550 signatures on Lentz's petitions could be challenged on various grounds, but a spokesman said it declined to do so in order to focus on issues.

The Republican Party of Pennsylvania said their candidate's petitions will be validated. "We remain confident that Pat Meehan's petitions, at the end of the day, are valid and he’ll be on the ballot," said Michael Barley, a spokesman for the party.