Fact #1: Obama's advantage with female voters is on-par with Kerry's support in 2004 at 54% -- 4% undecided or "other" To get the same level of support from female voters McCain would have to win the entire 4% of the uncommitted vote to get himself to 46% to match Bush 04.
Fact #2: Obama surges past Kerry's 04 support among men by 5%. 7% uncommitted. McCain would have to grab the entire 7% undecided and erode 3% from Obama's lead to match Bush 04
Fact #3: The most recent polls out of PA are under representing the black vote by as much as 3% Obama will win that 3% by an overwhelming margin and this is all assuming 08 turnout matches 04 turnout when in reality it will be much greater.
Fact #4: Obama is not drawing a significant amount of extra support among young voters in PA. He's presently on-par with Kerry 04 at 60% 18-29. So in other words, Obama is not relying on a flakey demographic to win the state. Obama does not need radically higher youth turnout to win. Again, McCain would have to win all 5% of the uncommitted voters to match Bush 04.
Fact #5: Obama is exceeding Kerry 04 in 65+ Yet again, McCain needs to win all 6% of the uncommitted voters and erode 1% from Obama to match Bush 04.
Fact #6: Obama has *double* the support among Republicans in PA as Kerry 04. McCain is grabbing an additional 3% of the Democratic vote in PA. Most likely angry Clinton supporters. One of the few bright spots in these numbers for McCain.
Fact #7: Only 12% of voters in 2004 made their choice in the proceeding week before the election. This suggests PA voters tend to make up their mind early. Only 10% made their choice in the month of October. 79% made their choice before October.
So in summary... Obama's advantages are across the board. There is no particular demographic McCain can target. McCain is facing large deficits from Bush 04 in almost every single demographic at a more or less equal rate. He would need an across the board surge of approximately 10-15% to win PA while there is a strong indication that PA voters are abnormally hard to sway in the closing 4 weeks of an election.