As one from the deep south who moved to the northeast (usually the other way around, and who retires to the north?; academia takes some to unplanned places), I want to offer my perspective on this. First, I enjoyed viewing the map, entertaining in fact, and in a suggestive way, an element of truth to it.
The only caution I have is the propensity for stereotyping. While I live deep in the eastern part of the rust belt, it is certainly not the bastion of "eastern establishment liberalism". There are plently of religious fundamentalists, staunch conservatives, and pardon the affectionate phrase, "rednecks" around. On the flip side, back in my former southern domain, which I visit quite often, there are an appreciable number of liberal minded, upscale citizens.
Certain areas may hold a majority for a particular political outlook, though the divide of differences may be in the single digits in terms of percentages.
The 2000 national election showed majority democratic support in urban, coastal, and muti-dimensional communities; while republican support dwelled strongest in the national interior, rural, and suburban environments. Obviously, Florida, with a combination of it all, showed us the confusion and divide regarding this.
The north-south divide has gotten blurred. In college sports, it recently happened; who would have thought Clemson and Boston College as sisters in the same division of the same conference ;D?