Democratic Votes by County (The Darker the Red, the higher Percentage Democratic):
http://uselectionatlas.org/RESULTS/img.php?year=2008&st=PA&pty=1&type=map_pty&off=0&fips=42&elect=0The same for the GOP Voters:
http://uselectionatlas.org/RESULTS/img.php?year=2008&st=PA&pty=2&type=map_pty&off=0&fips=42&elect=0http://uselectionatlas.org/RESULTS/Basically, Western Pa was the traditional Democratic Heartland of Pa, going back to the days BEFORE Lincoln. Philadelphia and Pittsburgh themselves were GOP Controlled for Decades (In Pittsburgh that ended in the 1920s with no GOP member on its City Council after 1934, Philadelphia stayed GOP till the 1940s, with its suburban Counties GOP Dominated till recently).
Furthermore the Red Counties in Western Pa are NOT that Red. McCain won Greene County by 68 Votes out of 14,816 casted. McCain Won Fayette by 160 votes out of 51,178 cast, yet on this map both are marked solidly Red. Cambria County is Blue but 716 votes for Obama then McCain out of 60,689 cast is NOT that great a margin. Beaver is just as Obama wining that county by 2600 votes out of 82,096 votes cast. Washington went for McCain 53% to 47% but that reflects the extension of the Pittsburgh Suburbs to Northern Washington County more then any other factor. McCain did better in the West then many other Republicans over the years, but to paint the counties solid red is a mistake. As you go further east the McCain percentage Climbs, but Clinton which is in the Middle of the State went McCain 51-49% (And it is a traditional GOP Area).
Now I should note that the GOP looked upon Western PA as an area they could grab in the 1990s as the older generation (i.e. People who had first hand experience of the Great Depression and WWII were dieing out, and their Children, now in their 50s, are more willing to listen to GOP arguments then their parents had been). The numbers are to close and reflect this push by the GOP then anything else. It is funny when you think about it, the senior citizens of today's Western Pa is more Democratic then their 50 something children, who are turn are bring followed by their more Democratic 20s something Children of today.