You already know all about swing states; today in the New York Times, Nate Silver introduces another important factor in the 2012 election: elastic states, which can produce difficult-to-predict results. Swing states, he explains, sometimes have very few swing voters (see North Carolina, where likely Democratic voters are fairly evenly matched with likely Republican voters and the election pretty much comes down to turnout), while elastic states are not necessarily swing states, but they do have a lot of swing voters. The most elastic state, by Silver's calculation, is Rhode Island.
Unlike North Carolina, Rhode Island's likely Democrat voters far outnumber its likely Republican voters—but, also unlike North Carolina, it also has a huge number of independent, aka "persuadable," voters. So, though it leans toward Democrats and is therefore not considered a swing state, if presented with a Republican option that is palatable enough, Rhode Island could turn red. (Massachusetts is also highly elastic, which explains Scott Brown's victory there.) Basically, elastic states are more "sensitive or responsive to changes in political conditions," Silver writes. So, if Obama's standing improves nationally, it will improve even more in an elastic state—and vice versa. Click for Silver's full explanation and state rankings.