If Joe Sestak vacates his U.S. House seat to run for U.S. Senate, Delaware County could become a focal point of state and national politics in 2010.

The 7th Congressional District, which encompasses most of Delaware County and portions of Chester and Montgomery counties, would become a nationally watched race, as Republicans attempt to take back the seat that Sestak won in 2006.

His stunning victory over 10-term Republican Curt Weldon made him only the second Democrat to win that district since the Civil War.

Some Democrats - particularly Gov. Rendell, who is strongly backing Sen. Arlen Specter in the Democratic primary - fear a replay of 1986, when Bob Edgar, the district's last Democratic congressman, stepped down to take on Specter in the general election. Edgar lost. He had won the House seat in 1974 amid the Watergate fallout.

"It's almost being a little bit selfish," Rendell said of Sestak's Senate aspirations. "He's a good congressman, and that would be a serious loss. I think Joe has a lot to offer in the Congress, and he should stay there."

Assuming that Sestak doesn't heed that advice, Democratic state Rep. Bryan Lentz plans to run as his replacement, which would give Republicans the opportunity to pick up Lentz's seat in the state House, where Democrats hold a 104-99 majority. Lentz is also in his second term in a district that had long been held by Republicans.

Federal prosecutor Craig Williams, who ran against Sestak last year, and Montgomery County businessman Steven Welch are among the possible Republican candidates in next year's 7th District race.

Some Republicans want former U.S. Attorney Pat Meehan, of Upper Darby, to scrap his gubernatorial bid and run for Congress. Meehan spokeswoman Virginia Davis said that the former Delaware County district attorney is "flattered" by the encouragement from party leaders to run for other offices, "but his focus remains on building an exploratory committee for governor."

Stuart Rothenberg, editor and publisher of the Rothenberg Political Report, said that next year's political environment likely would be less hostile to Republicans than past cycles, without President Bush dragging their numbers down or President Obama boosting the Democratic turnout.

Sestak was re-elected to a second term last year with 59 percent of the vote.

"You could see a very competitive race, even though Sestak didn't have a tough fight last time," Rothenberg said. "We often see incumbents win it big, then it opens up and you have a race."

Longtime Republican state Rep. Mario Civera's seat in Upper Darby also will be open next year. He's stepping down to run for Delaware County Council.

The results of the three races could indicate the county GOP's strength, or weakness, in the Democratic-trending Philadelphia suburbs.

Tom Judge Sr., who has run the party since 1975 - following the dissolution of the 15-member "War Board," which used to call the shots - plans to step aside in November. Andrew Reilly, a former County Council chairman, is his most likely successor.