Sen. Arlen Specter (D) and Rep. Joe Sestak (D) will make their first public appearance together in Pittsburgh at the Netroots Nation convention next week. The two Democrats will face off in a forum at the annual liberal blogger confab.

Sestak formally announced this week that he would challenge Specter in the Democratic primary. Specter announced earlier this year that he was switching parties to run for re-election as a Democrat.

According to the conference organizers, both Sestak and Specter will answer questions from journalists on a panel, plus questions that were solicited online in advance.

Costello Joins Race for Gerlach’s Open Seat

Chester County Recorder of Deeds Ryan Costello (R) announced he will run for retiring Rep. Jim Gerlach’s seat.

Gerlach is stepping down to run for governor, leaving his competitive seat wide open in 2010. State Rep. Curt Schroder (R) already announced he will run for Gerlach’s seat. Several other candidates are still considering a bid in the southeastern Pennsylvania district.

“We deserve better from our elected officials in Washington, DC than the blind following of party leaders,— Costello said in his announcement.

Democrats have already indicated that they plan to target the seat. Several Members of Congress have endorsed former editorial writer Doug Pike (D), the son of former Rep. Otis Pike (D-N.Y.), as their candidate.