If you place a map of the states that favoured the proslavery south over a map of the states that are now showing a trend for John McCain, you will get an almost perfect match. The only differences: Virginia has switched sides, and West Virginia has too. (It is now for McCain.) Florida, once part of the Confederacy, is also now prone to vote Democrat because of a massive influx from the north. The rest is essentially unchanged since the 1860s. Even in America, the past controls the present. [Emphasis mine]It would be foolish to deny that slavery and the Civil War exert their influence over present-day politics. But it's also foolish to suggest that the electoral map is "essentially unchanged since the 1860s."
In fact, the south wasn't a unified conservative bloc even in the 1860s. (In 1869, Georgia, Kentucky, and Louisiana voted for Horatio Seymour while the rest of the south backed Union war hero Ulysses Grant.) In the '30s and '40s, FDR swept the south twice, along with the rest of the country. In 1952 and 1956 the former Confederacy (and nowhere else) threw its electoral votes to that good ol' boy Adlai Stevenson. In 1960 and 1964 the region's votes split down the middle; in 1976 every southern state but Virginia backed native son Jimmy Carter. In 1992 and 1996, Bill Clinton won many southern states. (Fascinating historical maps here.)
In the last two elections, of course, the south has been homogeneously conservative. But that's an anomaly, and the idea of the former Confederacy as a unified and consistently reactionary voting bloc is an unwarranted capitulation to the fantasies of Karl Rove.