I hate to point out the obvious, but the decline in Obama's poll numbers aren't from the conservatives or liberals abandoning him - it's the exodus of independents that's doing the damage right now - almost a 50% swing, to the negative, in independents.
That might be true (it might also be the white guilters getting some buyer’s remorse that is driving his poll numbers down). But in 2012, the left-wing media will tell the GOP that to win they need to go left to attract the “independents” of Iowa and NH. The GOP will, as usual, believe them and start pushing the RINOs to the front in another attempt at building that big tent.