Although the Republicans carried five ex-Confederate states in 1928, the Republicans didn't start making inroads into the region until the 1950's, when it won four ex-Confederate states in 1952 and five in 1956.
However, the South really began to turn Republican during the 1960's. In his book The Winning Side: The Case for Goldwater Republicanism (Putnam's Sons, 1963), Ralph de Toledano noted a strong Republican trend in the Deep South during the 1962 elections. The Republican vote was especially strong in the growing suburbs throughout the region.
Athough the Democrats managed to hold on to power that year by relying on an odd base consisting of blacks and rural segregationists, their strength was already seeping away. Ten years later, in 1972, Richard Nixon became the first Republican candidate to carry every Southern state, and since 1980, the South has been a solid component of hte Republican coalition.
But the real question is why did they switch? It looks like a complete switch in a little over 10 years
Guess who was living in those suburbs? Republicans who moved down south from Yankeeland. I have said before, if you want to thank someone for turning the South into Republican territory, first thank the guy who invented air conditioning.
Although the Republicans carried five ex-Confederate states in 1928,
Those old crackers weren't going to vote for a Catholic, even if he was a Democrat.