interactive graphic by The New York Times. Don't miss it. It is amazing in its simplicity, elegance, and depth. It's also a lot of fun, as it allows you to create whatever scenario you like with the nine undecided states.
You should read it right before the latest posts by Nate Silver at FiveThirtyEight, where you can also see plenty of graphs and maps. The new visualization is timely, as it somehow provides visual evidence to Silver's logic and reasoning in a time when he is under fire from certain pundits that suffer from acute innumeracy.
The best summary of his little ordeal is aptly titled "People Who Can't Do Math Are So Mad at Nate Silver", but there are others, such as this one and this one, both written after Silver was admonished (justly, in my opinion) by the Times' public editor, Margaret Sullivan. This whole situation may be well a reaction to something that this review of The Signal and the Noise suggests: the kind of journalism that Silver and other database and precision journalists practice and are popularizing is a serious threat to the professional commentariat. Fortunately.