Since it looks like it's going to Pennsylvania, I thought I'd do a preliminary analysis of PA Congressional Districts, and their likely results.
UPDATE: Not that anyone's reading this, but since I figure Terry Madonna is smarter than me, a couple of changes.
Congressional District 1 (7 Delegates). This district includes Southwest Philadelphia, those parts of South Philly, Center City, and North Philly east of Broad Street, and many of the largely African American western suburbs of Philadelphia, including Darby and Chester. Represented by Democrat Bob Brady, the (white) chairman of the Philadelphia Democratic party, who has yet to endorse, the district is 45.9% Black, 33.0% White Non-Hispanic, 15.0% Hispanic (mostly the large Puerto Rican community in Kensington), and 4.9% Asian. Obama will certainly win this district. The question is whether the delegates will split 4-3 or 5-2 in his favor. He will need 65% of the vote to get five delegates out of this district. Given that half the electorate should be Black, this seems achievable, although the non-black population of this district, including large white ethnic populations in South Philly and the Puerto Ricans in Kensington, will not be as favorable to Obama as in the second district. Still, Obama will likely only need about 40% of the non-Black vote to get the fifth delegate. Prediction: +1 Obama (but possibly +3 Obama)
Congressional District 2 (9 delegates). This district, which includes West Philly, those parts of South Philly, center city, and North Philly west of Broad Street, Northwest Philly, and some wealth Montgomery County suburbs, is represented by Chaka Fattah, who supports Obama. Demographically, the district is very favorable to Obama - 61.2% Black, 29.9% White non-Hispanic, 3% Hispanic, 4.3% Asian. The White population in this district is much more amenable to Obama than that in the first district - much more liberal and white collar, much less blue collar and ethnic. Obama needs 61.5% of the vote, which he should get easily, to get 6 delegates here. He needs 72.5% to get the seventh. That seems achievable, given the demographics - assuming Blacks are 65% of the electorate, and he gets 85% of the Black vote, he'd need about 57% of the non-Black (mostly white) vote to get up to to a 7-2 split. That seems achievable, but for the moment, I'll be cautious, and assume a 6-3 split. Prediction: Obama +3 (but Obama +5 a distinct possibility)
Congressional District 3 (5 delegates). This district, represented by Republican Phil English, comprises most of northwestern Pennsylvania - Erie, Crawford, Mercer, Butler, Armstrong, and parts of Warren County. It is almost entirely white - 93.7% non-Hispanic white. This seems like the kind of blue collar, Appalachian district where Clinton will do well. She will easily win three delegates here. She would need 70% of the vote to get four delegates - her performance in Youngstown, etc., in Northeastern Ohio wasn't quite this good - she'd have to have a very good day to get the fourth delegate. Prediction: +1 Clinton
Congressional District 4 (5 delegates). This district, represented by Democrat Jason Altmire, who has not endorsed, comprises northern and northwestern suburbs of Pittsburgh. It is also over 90% White, and once again, is the kind of Appalachian white blue collar area where Clinton ought to do well. Here, I'd say, she has a better chance for four delegates than in district three - some of the adjacent Ohio counties did go for her by that margin. Still, she needs 70% to do that, which is difficult. Prediction: +1 Clinton.
Congressional District 5 (4 delegates). This district, represented by Republican John Peterson, occupies an enormous swathe of north-central Pennsylvania. It's 96.5% White, and most of the area ought to be Clinton country, but it also includes the college town of State College (yeah, creative name, I know), where Penn State is located. Given that it's only four delegates, and with the presence of State College, this one ought to be split evenly. Prediction: Even split
Congressional District 6 (6 delegates). This district includes relatively wealthy Philadelphia suburbs in Montgomery and Chester Counties, and kind of exurban sprawl in Berks County. It is represented by Republican Jim Gerlach. The district is 89% White, and more Republican than the other Philly suburbs, given the exurban, Chester and Berks County portions. I assume Clinton will have the advantage here. She needs 58.5% to go from an even split to a 4-2. Holding this district to a split is pretty essential to Obama, I think - he needs to do relatively well in the Philly suburbs, or he's doomed. Prediction: Split
Congressional District 7 (7 delegates). This district, represented by Democrat Joe Sestak, who has endorsed Clinton, comprises the majority of Delaware County, although the parts of the county with large numbers of African Americans are in District 1. Demographically, it looks fairly similar to the 6th District - 89% White. With seven delegates, Clinton ought to pick up a one delegate advantage here, but she'd need 65% to get up to 5 delegates, which seems unlikely. Prediction: +1 Clinton. (UPDATE: Madonna seems to think the Philly suburbs should be good for Obama, so I'll switch to +1 Obama)
Congressional District 8 (7 delegates). This district, represented by Democrat Patrick Murphy, comprises the Bucks County suburbs of Philadelphia. It is 92% White. Like the other Philly suburban districts, I assume this one leans Clinton, but like the 7th, it should be difficult for her to get up to 5 delegates. Prediction: +1 Clinton (UPDATE: Likewise, +1 Obama)
Congressional District 9 (3 delegates). This district is a vast Pennsyltucky district in South central Pennsylvania, stretching from the outskirts of Harrisburg to Altoona and Connellsville. Represented by Republican Bill Shuster I can't imagine Clinton not winning two delegates here. Prediction: +1 Clinton.
Congressional District 10 (4 delegates). This district in northeastern Pennsylvania includes Carbondale and Williamsport. It is currently represented by Democrat Chris Carney, who has not endorsed. The district is the whitest yet - 96.3%, and contains no notable segments of Obama friendly population that I can discern. This is one where I would think Clinton stands a real chance of getting the 62.5% necessary to secure a third delegate. Prediction: +2 Clinton
Congressional District 11 (5 delegates). This district includes Scranton, Wilkes-Barre, Hazleton, East Stroudsburg - i.e. the more Democratic parts of Northeast Pennsylvania. It is represented by Democrat Paul Kanjorski, who has endorsed Clinton. Once again, a vastly white, blue collar district - Clinton has to have the advantage here. Predicton: +1 Clinton
Congressional District 12 (5 delegates). This oddly shaped district that runs in a very weird way around western Pennsylvania, was designed to be a safe seat for Democrat John Murtha, who has not endorsed. Once again, very very white, and blue collar. Prediction: Clinton +1
Congressional District 13 (7 delegates). This district includes parts of (largely white, blue collar) Northeast Philadelphia, as well as some well off Montgomery County suburbs. It's represented by Democrat Allyson Schwartz, who has endorsed Clinton. 87% White, I'm going to assume, again, that Clinton will have the advantage here. Prediction: Clinton +1. (UPDATE: Likewise, switch to +1 Obama)
Congressional District 14 (7 delegates). This district includes Pittsburgh and its inner suburbs. It is represented by Democrat Mike Doyle, who has not endorsed. It's 22.7% Black and only 1.1% Latino, and heavily Democratic. This ought to be a good district for Obama. Prediction: Obama +1
Congressional District 15 (5 delegates). This district comprises the Lehigh Valley - Allentown, Bethlehem, Easton. Represented by Republican Charles Dent. Largely white, but with a significant (8%) Hispanic population. Prediction: Clinton +1
Congressional District 16 (4 delegates). Mostly Lancaster County, but also snakes around to include Reading. Very very Republican, and represented by Republican Joseph Pitts. 88% White, with a significant (9%) Hispanic population. Clinton will probably win, although likely by not enough to secure a third delegate. Prediction: Split
Congressional District 17 (4 delegates). Includes Harrisburg, Lebanon, and Pottsville. Represented by Democrat Tim Holden, who has not endorsed. A decent sized Black population (7.5%), which ought to be a considerably larger portion of the Democratic electorate, suggests that it will probably be a split, whoever wins. Prediction: Split.
Congressional District 18 (5 delegates). This district includes southern and eastern Pittsburgh suburbs, and is represented by Republican Tim Murphy. Vastly white, and probably mostly Republican. Presumably it's advantage Clinton. Prediction: Clinton +1
Congressional District 19 (4 delegates). This very Republican district, which includes York, Carlisle, Gettysburg, and Hanover, and is represented by Republican Todd Platts, seems likely to be a split. Prediction: Split.
This doesn't come out looking great for Obama. Depending on how Philly turns out, it's somewhere between +3 Clinton and +7 Clinton.
In terms of areas for improvement for Obama, besides the two Philly districts, the Philly suburbs would present themselves as the obvious places. Anyway, the basic result is: Pennsylvania's going to be very difficult for Obama. As it stands, he looks likely to win only three of Pennsylvania's 19 congressional districts.
I will admit, though, that my demographic command of this is somewhat dubious - Perhaps I am overlooking likely blocs of Obama support in the non-Philadelphia and Pittsburgh portions of the state. Please comment and let me know.
UPDATE: So, if we give Obama the three Philly suburban districts with odd numbers of voters, we actually switch to a range of +3 Obama to +1 Clinton, apparently...pounding the Philly media market (which also includes the Lehigh Valley, where Madonna also seems to think that Obama has a shot) might be the key for Obama. There aren't any delegates to be had in Harrisburg, York, and Lancaster, so really Philly and the Lehigh Valley is where Obama needs to get margins. If he can manage landslides in Philadelphia proper, and wins in all the Philly suburban districts plus maybe the Lehigh Valley, and also win Pittsburgh proper and prevent Clinton from getting landslides in the west and northeast Pennsylvania districts, he can win the district by district delegates.