A lot changed in 1980.
I have traditionally been non-political, though my interest was piqued by the rise of the Radical Religious Right circa 1980 and the dire threat it posed for religious liberty. And then a few years ago my friend * re-introduced me to the term, "Dixie-crat".
Abraham Lincoln was a Republican. So was his VP successor, Andrew Jackson. So were the many officials, AKA "carpet-baggers", who moved into the South after the Civil War and who are universally and totally hated Down Thar. As a result, all Republicans were reviled and Southern politics were dominated by the Democratic Party. And the Democratic Party in the South was concerned with maintaining that status quo and keeping segregation alive and well.
Now the shift. First there were the Kennedy/Johnson initiatives and the 1964 Civil Rights Act. A lot of the resistance to civil rights came from the "Dixie-crats". Later (from a PBS program by Bill Moyers), after a lot of the civil unrest had died down, especially after Nixon's resignation, President Jimmy Carter had convened a conference on the family in order to encourage dialogue for determining what needed to be done for families.
That back-fired (again, drawn mainly from a Bill Moyers program). The Carter treatment of family was to greatly extend it beyond "traditional" parameters. As Moyers had presented it, Southern religious values were still associated with the Democratic Party for the most part. Carter was a self-professed "born-again Christian", which had drawn the conservative Christians in to support him. But now with this conference on the family and what its findings were developing into, many conservative and fundamentalist Christians were finding that they just could not buy into that.
Then came 1980. Reagan courted the newly formed Radical Religious Right who embodied and galvanized the newly dis-illusioned conservative Southerners. Basically, it was in 1980 that the South shifted massively from Democrat to Republican. The Southern Democrats felt that they had been betrayed by Jimmy Carter and his party and they jumped onto the Republican ship. Which is now sinking.
FOOTNOTE *:Liberal. In our particular dark red hole of California, Republicans and fundamentalist Christians tend to predominate, so she was very pleasantly surprised to learn that I was most decidedly neither. With so many of her other friends, she had to first carefully syncopate her way through elaborate dances with them trying to get a feel of where they stood on things.