This post has been updated.

WASHINGTON – Bucks County Congressman Mike Fitzpatrick is retiring -- and his brother is now hoping to replace him in Pennsylvania's most competitive congressional district.

Brian Fitzpatrick, a former FBI supervisory special agent, is planning to announce his run Thursday afternoon in Doylestown, confirming long-running rumors that he will seek to replace his brother, a Republican who has held the seat for four-terms.

The announcement is planned ahead of the county GOP's first endorsement screening, scheduled for Thursday night.

Brian Fitzpatrick's plans have been subject of rumor for some time. The congressman told a Bucks County Courier-Times reporter last month that his brother was considering a run, and the Capitol Hill newspaper Roll Call reported that Brian Fitzpatrick had moved back to Pennsylvania after working with the FBI in California in advance of a potential run.

Neither the congressman nor the chairwoman of the Bucks GOP have returned messages seeking comment.

Republican state chairman Rob Gleason and former Bucks County Commissioner Andy Warren, who himself is running for the GOP nomination, both said they were told Brian Fitzpatrick would be among five candidates screening before the Bucks County Republican party.

The candidates are seeking the party nod in a race targeted by both parties' national arms, for a seat that hasoften flipped between Democrats and Republicans.

"Fitzpatrick's brother has been making phone calls saying he will be screening on Thursday night, too," Warren said.

"I heard that he's going to run," said Gleason.

Other Republicans running are state Rep. Scott Petri, who has rolled out a string of party endorsements, Dean Malik, a former Bucks assistant district attorney, neuropsychologist Marc Duome and Warren.

Mike Fitzpatrick is in his fourth term in the eighth district, which includes Bucks and a small piece of Montgomery County. He is not running for re-election after promising to limit himself to four terms. But he had about $1.1 million in his campaign fund as of the end of September, a substantial amount that could help another candidate.

Gleason said he does not know Brian Fitzpatrick, but that the name carries weight.

"People vote names," he said. "They're comfortable with certain names and they vote for them."

Democrats also have a primary: state Rep. Steve Santarsiero and businesswoman Shaughnessy Naughton are competing for the nomination.

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