if thats based on whos betting on mccain...thats probably because its a betting website and they're giving him better odds. its like when someone beds on a 20-1 longshot in a horse race.
http://www.fivethirtyeight.com is where you need to go. they take ALL the polls and evaluate them as a whole. these are the statisticians that handle major league baseball and things of that nature. stats are their job.