Rep. Jim Gerlach has told National Republican Congressional Committee officials that he is running for governor, a GOP source confirmed Tuesday, making his competitive southeastern Pennsylvania district a prime Democratic pickup opportunity in 2010.

The Allentown Morning Call first reported that the four-term Republican has opted to run for governor, ensuring that his suburban Philadelphia 6th district seat will be a top battleground next year. According to the newspaper report, Gerlach is expected to make his gubernatorial announcement at some point Tuesday.

Gerlach won re-election last year against a little-known opponent by a slim margin in the Democratic-leaning district. Democrats have targeted Gerlach’s district for several cycles, often spending millions in independent expenditures in an effort to defeat him.

Former editorial writer Doug Pike (D) has already announced his candidacy for Gerlach’s seat, plus Democratic sources say he is willing to put $1 million of his own personal wealth into the race.

Republicans, on the other hand, will have a harder time finding a top candidate who can hold the seat like Gerlach has. State Rep. Curt Schroder (R) has indicated that he will likely run if Gerlach runs for governor.