From Nate Silver.
If you don’t know who Nate Silver is, he’s just about the best odds-maker / statistician in the business.
Look at this image.
It should tell you everything you need to know.
If you still don’t get it, click here and Nate will explain it to you.
http://www.fivethirtyeight.com/2009/12/why-progressives-are-batshit-crazy-to.html