Much has been written about this matter.<quoted text>
If you recall, the South is Republican today. The same folks who were Democrats back then.
Gosh remember Wallace et al. From Wikipedia:
After the signing of the Civil Rights Act of 1964, the old argument that all whites had to stick together to prevent civil rights legislation lost its force. More and more whites began to vote Republican, especially in the suburbs and growing cities. Newcomers from the North were mostly Republican; they were now joined by conservatives and wealthy Southern whites, while liberal whites and poor whites, especially in rural areas, remained with the Democratic Party.
A huge portion of Representatives, Senators, and voters who were referred to as Reagan Democrats in the 1980s were conservative Southern Democrats. An Interesting exception has been Arkansas, whose state legislature has been continued to be majority Democrat (having, however, given its electoral votes to the GOP in the past three Presidential elections, except in 1992 and 1996 when "favorite son" Bill Clinton was the candidate and won each time) until 2012, when Arkansas voters selected a 21-14 Republican majority in the Senate.