Murtha is in a Solid Democratic District, extending from Green County (Heavy Democratic do to a lot of Coal Miners) Southern Washington County (Ditto) but Northern Washington County is becoming a Suburb of Pittsburgh, and as such heavily Republican. Technically the Plaintiff lives in Cannonsburg, a Suburb of Washington PA on the old road to Pittsburgh, but along how the suburbs have been extending since the 1980s.
Now when the Republicans in the State House redrew the Congressional Districts in 2000 they had a problem. Western Pa has been heavily Democratic since before the Civil War. The big exception to this rule prior to 1928 was the City of Pittsburgh itself. In the year the Democrats finally won the Mayor's office and by 1932 NO Republicans was on the City Council (and no republicans have been on the City Council since 1932). This reflected the fact the rural areas had always been Democratic in Western Pennsylvania AND the shift to the Democratic Party all Cities went through during the Great Depression and afterward.
After WWII most Republicans moved to the newer Suburbs, where they had a chance of being elected. thus the suburbs, while still Democratic, are more evenly divided between the parties then the City AND the old rural Coal mining areas. Thus the GOP dilemma in 2000, how do you make a GOP area out of this mess? The GOP did what it had done in 1980 and 1990 when it controlled the State Government, it used the latest computers to design a district with as many Republicans they could in it and still be "one district". In 1990 this resulted in a a Semi-Circle around Pittsburgh extending into Northern Washington County and Western Westmoreland Counties, In 2000 that was no longer possible do to population lost in the area so a district had to go, which meant a shift eastward of all the districts.
How the GOP did this was took Murtha District which had been centered on Johnstown and shifted as many Democratic areas into they could. He lost Eastern Westmoreland County and given Greene County AND the Monongahela Valley of Washington County (Heavy Democratic area), Murtha's district was extended to include heavier Democratic Washington PA and while as Indiana PA, but the areas north South (and in the case of the City of Washington West, in the Case of the Borough of Indiana East) so these ended up a little peninsula extending from his district. Furthermore they gave him the Kiskiminetas Valley, like the Monongahela Valley an area of old industry and heavily unionized and Democratic.
The 18th Congressional District is between Murtha's District and Pittsburgh was given the new Suburbs of Northern Washington County AND Western Westmoreland Counties, most of Indiana County (Rural non-coal mining areas) and the furtherest Suburbs in Allegheny County (County Seat is Pittsburgh). Even with these areas the District had more Democrats then Republicans but it was close enough for the GOP to think they could win it (and they still hold that seat).
Notice the City of Washington PA and the Borough of Cannonsburg are in Murtha's district, but north, south and West of that little dot, Washington County is in the 18th District. Murphy, the GOP congressman who present represents the 18th District is running again, and given how Washington County has become more GOP since 1990 (do to the expansion of the Pittsburgh Suburbs) he has a good chance, and I believe this is more to help Murphy then hurt Murtha. Murtha's district is about 60% Democratic, the chances of his Republican opponent winning is somewhere between slim and nil, but in the 18th District it is a different ballgame. I believe the plan is to paint Murtha with being anti-military and associate Murtha with Murphy's Democratic Opponent. Thus why this lawsuit came out NOW, it is to help Murphy get re-elected NOT to help defeat Murtha.
Murtha's 12th District:
http://en.wikipedia.org/wiki/Pennsylvania_Congressional_Districts#Twelfth_Congressional_District18th District:
http://en.wikipedia.org/wiki/Image:PACongressionalDistrict18.pngStats on PA districts: