You have the opposite margins for Carter on that graph. (Should be D+6.9 and D+2.5).
Also, the "Southern Strategy" is largely a myth; if you actually read The Emerging Republican Majority you see that the Nixonians' strategy was almost entirely focused on attempting to flip large northeastern and midwestern urban areas, while almost no attention is paid to the South besides assuming that the "New South" of VA, FL, and TX will flip on its own because of economic issues.
Kevin Phillips spoke of a strategy in the "Outer South" to capitalize on a sense of disconnection from the liberal causes of the national Democratic Party establishment.
It's been a couple years since I read it but I remember being struck (given my expectations) about how little space he devoted to discussing the South; IIRC more of the book is devoted to discussing Maryland than the entire South combined. As I recall even Massachusetts received quite a few more pages than any Southern state.
