The math is real, real simple. Obama is below 45% re-elect in the States of Florida, Virginia, Indiana, North Carolina, and is sitting at 46% in Ohio.
If those States do not vote for him in 2012, he will only have 273 Electoral Votes from his remaining 2008 States. Enough to give him the win... but he has to swing everything to win it!
This puts him in a corner.
If he loses any State more than the five listed above, he cannot win. Period.
Did you factor in the movement of electoral votes?