This is data visualization gone wrong. I am afraid you have drawn a wildly incorrect conclusion because the programmers were too lazy to deal with the political and historical inconvenience of Gov. George C. Wallace, the Southern Dixiecrat and presidential nominee of the American Independent Party. Alabama didn't suddenly take 73% a left turn to vote for LBJ's vice president in 1968; they, along with Mississippi, Louisiana, Georgia, and Arkansas, voted for George Wallace, a candidate who made Richard Nixon look like Bob Dylan in comparison. Get the facts:

http://uselectionatlas.org/RESULTS/national.php?year=1968...

The moral of the story (in my mind) is that while it's tempting to throw a big dataset into a cool visualization algorithm, if you're not careful about what each individual data point means, you might end up imparting more confusion and misconceptions than actual knowledge.