It matters perhaps that these are states (VA, NC, and GA; less so SC) that have way more transplants and in-migration from the northeast than anywhere else in the South, except maybe Florida, which is sui generis.
That's true, in the sense that SC whites are about 25% Democratic, as opposed to AL whites which are about 12%. But certainly given past history there is very little reason to believe that any national Democrat will win much more than 25% or so of such whites (Sheheen got about 28%), and especially not registered Republican whites, which vote about 97% for the Republican.