The registration edge for Dems in PA is that big?? Very surprising considering their congressional delegation usually tilts Republican and I think the GOP has controlled the legislature for most of the recent past. The state is certainly very purple so it must be that a lot of those registered Dems vote Republican in many elections. So I am hopeful Mitt can eke out a win there. If so he will almost certainly take the presidency.
Actually of those identifying as Republican vs. Democrat (including leaners), Gallup has PA with a D+5 edge (in 2011). That’s a large swing from 2009. You can see those statistics as well as other states from this link:
http://www.gallup.com/poll/125066/State-States.aspx