There's a growing sense among strategists in both parties that two distinct, even inverse, sets of swing states now hold the key to close presidential elections.
One set includes the traditional battlegrounds of American politics: the metal-bending behemoths of the Rust Belt like Ohio, Michigan, Pennsylvania and Wisconsin. These states tend to be older, preponderantly white, and stagnant or declining in population.
The emerging battlegrounds are their opposite: fast growing, diverse, generally younger states across the Sun Belt. Many of these states were solidly Republican in the 1990s, but have grown more competitive as their population has tilted more toward racial minorities and socially-moderate college-educated whites.
President Obama won most of both groups of states in 2008, but his path in 2012 looks much more challenging.