On top of the fundraising advantage, Clinton is increasingly on the defensive to justify her campaign, which may be another reason to explain Obama's mini "surge". On the other hand, the national polls don't seem to indicate that, with the last four offerings all within the margin of error:
Obama was pulling away, and it looked to be a trend, but since then the gap is back to a virtual stalemate.
On the whole, good signs for Obama in Pennsylvania, if he could ever pull out a win, the race would be over, given the expectations. In reality, a close result also works for Obama, because anything less than a decisive win for Clinton, in a state she needs desperately, and the calls for her to pull out will reach crescendo.