I know a lot of folks have been biting their fingernails to the quick with worry over the latest national polling data. However, the state polls have been pretty friendly to Obama. Why the discrepancy? The national polls have a pretty reasonably sized margin of error; most of them sit around 2 to 4 percentage points. The state polls also have a pretty good sized margin of error, but taken together, the margin of error is much smaller.
What I decided to do was treat the state polls as a decomposed national poll. I used FiveThirtyEight's averages for the individual states and used the popular vote totals from 2004 to weight them. While I realize that that underestimates the possible Democratic enthusiasm/Republican malaise effect that could occur in this election, this also provides a pessimistic estimate of the results come November 4th (or November 5th if you're a Democrat in Hampton Roads {j/k}).
The results provide what I believe to be an accurate picture of the popular vote situation.
Obama McCain
63868213 56619470
53.0% 47.0%
So we see that Obama has about a 6-point lead in the aggregate. I think this is pretty close: McCain is running up huge margins in states which Obama has essentially conceded, while Obama is keeping things close in some states which have been traditionally Republican.
If anyone wants to see my spreadsheet, let me know.