I should point out that I was going more by historical data in my comment on suburbs. Suburbanization was largely responsible for states like Virginia, Tennessee, Florida and Texas swinging towards the Republicans in the 50s and 60s.
Oh yes, in that sense it's valid.
And what is interesting is of course that this de-Southernization of certain states which made them more Republican friendly in the past is now taking them in the other direction, so that Florida and Virginia were actually Kerry's best states in the South, despite the fact that neither voted for Clinton in 1992 (and Virginia of course not even for Carter).