Question: What was the only district to vote for John Kerry in 2004 and John McCain in 2008? Answer: Pennsylvania's 12th District, which was represented by the late John Murtha.
This district will be filled by a special election that will likely be March 18. In a race between a generic Democratic and a generic Republican, the Republicans wins this seat. We'll have to wait and see who runs. There could be a very locally-connected Democrat, but the current mood and the trends both favor the GOP.
This is class "Deer Hunter" country: It's heavily unionized and socially conservative. This means the classic voter here is a guy who works at the steel mill 9-5, Monday through Friday, hunts on Saturday, and goes to Mass and roots for the Steelers on Sunday. His name could be Kovar, Halloran, Gryzbowski, or Lombardi.
In every primary and general election since 1945, Democrats hold "the rally in the valley" at the Slovak Home in Monessen, steel town on a bend on the Monongahela River. According to the Pittsburgh Tribune-Review, "Attendance is de rigueur. Amid the cigarette smoke and the smells of kielbasi, sauerkraut and beer, Democrats fill every inch of the hall listening to speeches and stirring interest in what has been declining voter turnout over the past 20 years."
As the district ages and empties, it's becoming more Republican. The GOP drew this oddly-shaped district in 2001 to accommodate Murtha, who was the second ranking Democrat on the Approps Committee. Republicans had a 12-7 majority in the Pennsylvania delegation at the time, but Democrats have flipped that to 12-7 in their favor today.
This district hasn't changed much since Murtha was elected in 1974, but the circumstances around it have. It's now to the right of the state, the country, and Obama. This election will be a good measurement of the resolve of the United Mine Workers and United Steelworkers (the de facto Democratic machines here) and of the strength of Republicans in this region.