Every cycle since '00, the Republicans make a major push at PA, especially as each campaign draws to a close. In '12, PA looked like it was solidly in the Democratic column, until some late polls started showing Romney making a small dent. Then, the Romney camp made a major push there to no avail, losing by >5 points. In '08, PA really wasn't that close and yet the Republicans tried hard. Bush made the most serious charge in '04, trying to draw enough conservatives between the east/west borders to offset the margin in Philly and it failed, although it was close (2.5 points).
It seems (that at least in a presidential year), as long as Democrats receive at least 80% in Philly, the Republicans have little chance. Sadly, the Republicans have gotten stronger in west PA, and it hasn't mattered.
Why are they fooled each time? I know the state ends up as "competitive" compared to others, but it's not budging.
PA is about D+2 or D+3 so if the national polls are close PA will look close.