Nate Silver said:Then again, the story of Thursday’s polls wasn’t all that complicated: Mr. Obama held leads in all six of the polls released of voters in Ohio, Florida, Pennsylvania, Wisconsin and Michigan — and Mr. Romney will need to win at least two of those states, and possibly three, to have much of a chance in the Electoral College. Mr. Romney has had some strong polling days recently, but this was not one of his better ones.
http://fivethirtyeight.blogs.nytimes.com/2012/08/24/aug-23-seven-ways-to-evaluate-a-poll/