As I’ve discussed before, in 2008 the red/blue map was not redrawn; it was more of a national partisan swing:
I also posted some graphs of previous vote swings that were less uniform.
But maybe it makes sense to study this more systematically. For every pair of consecutive elections since 1952 (that is, 1952/1956, 1956/1960, . . . , 2004/2008), I compute the interquartile range (that is, the 75th percentile minus the 25th percentile) of the swings in statewide vote proportions for the Republicans. I exclude third-party votes and also exclude states that were won by third parties. For each year, I computed the interquartile range for all 50 states (plus D.C. when appropriate) and also just for the non-southern states. Here’s what I found:
The past several decades have seen a steady decline in the variation of statewide vote swings. (The big spike in the graph is 1976, when Jimmy Carter did very well in a bunch of southern states that Nixon carried in 1972.)
To put it another way, the red-blue map is much more stable from election to election than it used to be. What’s going on? I’m not sure, but I think this is an important stylized fact.