U.S. Rep. Jim Gerlach (R-West Pikeland) is considering a run for governor in 2010, and while political watchers may disagree about the viability of his candidacy, one thing is certain: A decision by Gerlach to vacate his 6th Congressional District seat would open a huge window for Democrats.

Gerlach is in the unenviable position of being a Republican representing an increasingly Democratic district. Despite his reputation as a moderate, success in one election cycle has hardly allowed him to cruise in the next. After beating Democrat Dan Wofford, the son of former U.S. Senator Harris Wofford, by less than three points to win the seat in 2002, he was twice pushed to the limit by Lois Murphy, edging her by two points in 2004 and by 1 1/2 points in 2006. Even against a less threatening opponent this year, Bob Roggio, Gerlach only won by four points.

"He's had a tenuous hold on it," G. Terry Madonna, a pollster and political science professor at Franklin & Marshall College in Lancaster, said of Gerlach. "Somehow, he's found a way to win.

"I think it gives the Democrats a huge opening should he actually run," Madonna added.

The district is largely made up of areas in Chester County, where Democrats have made big gains in recent years, culminating with the capture of two Harrisburg seats this fall and a Democratic presidential vote for the first time in decades. It also includes parts of Montgomery and Berks Counties.

Though Gerlach is likely several months away from making any decisions about 2010, a vacated seat would open the floodgates for candidates on both sides of the aisle, from county commissioners up to state Senators.

Michele Vaughn, who chairs the Chester County Democratic Committee, said one person had approached her about the possibility of running, but would not say who.

"The district is socially moderate and fiscally conservative, so I think a candidate that fits that profile as a Democrat would be attractive," Vaughn said.

There are a number of Democrats who could throw their hat in the ring regardless of what Gerlach does, including state Sen. Andrew Dinnniman (D-West Whiteland), who until recently was one of only two Democratic state lawmakers in Chester County.

Chester County GOP Chair Skip Brion said he had not yet been approached by any potential candidates. He said a Republican candidate in the moderate mold of Gerlach could hold onto the seat.

"Each time, Democrats thought they could win that seat and they did not," Brion said.

• See also on PolitickerPA.com: Schroder interested in Gerlach's seat