Bryan Howerton will probably give you a much better and informative/documented answer. However, from my "experience" in researching Civil war vets buried in OK, many of the men from AR served in both CSA and USA (in that order), "switching sides" in late 1863. I believe it had a lot to do with the way the war was going. Gettysburg, Honey Springs, political situation, split loyalty to start with, etc.

This is a bad analogy, but....I ran track at University of Oklahoma and was on a national champion relay team. I went to grad school at Oklahoma State University and taught school in Stillwater for 23 years. I felt tremendous loyalty to OU my two years there and many years after. 28 years in Stillwater has made me more a fan of OSU, even with my history at OU. (Like I said, bad analogy, but shows how loyalties can change.)

Or women democrats who now are leaning towards McCain because of Palin because she's a woman (or men because she's good looking).

It can get complicated, but there is probably a much more simple answer than we will come up with.