It started for the most part in the 60s and 70s. Growing up in Tennessee during that time (and you have to remember that culturally traditional values are HUGE in that part of the country, what with it being the Bible Belt and all), as the Democrats became more and more wacko on social, cultural issues you did begin to see a marked shift in voting patterns during that time.
Oh, and don't forget the effect of Jimmy Carter's disasterous presidency.
The Democrats were always wacko on social and cultural issues. The intrusive Jim Crow Democratic regimes were a blot on American ideals.
The GOP from Lincoln to today has been the natural opponent of the Democratic politics of division.
I think you are on to something there but it isnt the complete story. Why and when did the Republicans of the North switch to Democrats?