I did a EV map based on Gallup's Aug 8 state-by-state presidential approval poll (
http://www.gallup.com/poll/148874/obama-job-approval-higher-states.aspx#2). At the the time of the Aug 8 polling, Obama's approval was 47%. According to Gallup, it is now 43%. Given historical precedent, no sitting president with an approval rating under 49% has won reelection (Bush II won in '04 with 49%, Ford lost in '76 with 48%). Therefore, I set as a premise that if Obama's approval in any state is 49% or more, he wins the state, 48% or less and he loses it (I actually added 1.5% to the presidential approval in every state). After adding the 1.5% to every state, I then subtracted 4% from his approval rating in every state as his Gallup approval has dropped that much since Aug 8, giving Obama a net -2.5% approval rating in every state from the Aug 8 poll. From there I looked at the percent of each state that was undecided. Of the undecided, I generally divided them 50% for and 50% against Obama, meaning if the approval rate was 45% in a given state with 10% undecided, I simply added half of 10% to the approval rate for a total of 50%. I altered this formula slightly in states with higher partisan ratings, so undecideds in Massachusetts went slightly more pro-Obama than the average.
An example of a surprising result: Oregon's approval was 44-48 on Aug 8. Adding 1.5% for historic incumbent advantage and subtracting 4% for the decline in approval, you get a current estimated vote of 41.5-50.5. I then split the 8% undecideds either 5-3 or 4-4, either way the approval was 46.5-53.5 or 45.5-54.5 and resulted in an Obama loss.
States that ended up within 1% of 50% I highlighted in 30% shade, just so they stood out easier. Overall it went GOP 317- Obama 221. Subtracting out the 1% states, it went GOP 281- Obama 215.
