If you want to see what momentum looks like in what has suddenly become a battleground state, look no farther than the Franklin & Marshall poll data for Pennsylvania.  The CBS affiliate in Philadelphia reported the results this morning, showing Barack Obama with a four-point lead in a state that Democrats cannot afford to lose under any circumstances — but just might:

A new Franklin and Marshall Poll shows that Republican Mitt Romney is now within striking distance of President Obama in Pennsylvania.

Less than a week before election day, the Franklin and Marshall College Poll shows Romney now trailing Obama by just four percentage points among likely Pennsylvania voters – 45-percent to 49-percent, compared to a nine point deficit in a September F&M survey. Poll director Terry Madonna says Romney is closing in, but he may be running out of time.

We’ll get back to that in a moment.  Take a look at the graphic from the poll report, though, showing the history of the head-to-head polling in this race:

This is the first time in the series that Romney has gotten out of the 30s, jumping up 5 points in a month.  At the same time, Obama has lost a couple of points, which could be within the margin of error, Still, that’s a change of seven points in the gap in just a month, and shows why Team Obama has begun spending money in Pennsylvania playing on the defense.

Let’s look again at the two key indicators in this election.  Among independents, Romney has a sixteen point lead, 48/32.  Ten percent goes to “other,” with another 10% undecided.  Assuming most of the undecideds break away from the incumbent — as is the norm — Romney might easily score a majority.  Obama won this demo in 2008 by 19, 58/39.

Next, let’s look at the gender gap.  Obama has the advantage here, winning women by 14 points, but losing men by six for an overall +8.  In 2008, Obama won men by three and women by 18 for an overall +21 in the gender gap.

Finally, let’s take a look at the sample.  The D/R/I in this survey is D+13 at 50/37/11, which tracks fairly closely to party registration but not to turnout.  In 2008, the D/R/I was 44/37/18 in a Democratic wave election, and in 2010 it was 40/37/23.  If the turnout comes closer to 2010 with these internals, Obama may be in bigger trouble than this poll indicates.