So, how could the United States end up with a different core set of swing states during presidential elections?
For instance, how could states like California, Illinois, and Texas be more swingish? Or regions like New England and the Deep South?
On the flip side, how could the seminal swing states Florida and Ohio be less swingish, and more firmly in the camp of one party (in Ohio's case, like how Missouri went from a bellwether to a lean Republican state)?
PODs can be whenever you want, but preferably in the late 1980's and 1990's or later.