The largest factor (aside from the Democrat party lurch to the far left on military and foreign affairs issues in the late 1960s) is likely the population shifts that occurred during the decades after WWII when white Republican professionals from Norther States began relocating to the South. (Thanks to air conditioning and the Cold War growth of the military and areospace industry in that region.) Guys with names like Gingrich, Barr and Bush. I have a number of friends and family members who are among those imported "Southern Republicans" and trust me, they have absolutely no relationship with the FDR New Deal segregationist Democrats who ran the "Solid South" of my youth.
The more slavery spread, the more diminished northern political power became with slave state whites outweighing them disproportionately due to things like the 3/5ths compromise etc
Kind on a confusing argument since the 3/5ths compromise only really mattered in congressional apportionment. Slaves, be they in Alabama or some new State, counted exactly the same in terms of congressional seats. How would spreading that slave population out over additional states effect the balance of power in Congress?
I remember being with my daddy and talking to Jamie Whitten and Sonny Montgomery about the massive switch and yes....at least in Mississippi it was largely due to Lott and Bill Waller as governor in the 70s.
The Yankee migration south first hit Texas oil patch in the early 80s and the later Yankee migrations were later and have done the exact opposite of what you claim.
They have enhanced the Democrat party here today...primarily in metro Atlanta, Piedmont North Carolina and here in Metro Nashville and of course Florida that used to be reliably Republican.
The rest of Dixie is not terribly affected by Yankee migration and the white voters are more GOP than anywhere this side of Utah.
Dang Ditto....you must be younger than I thought.
We are mostly whites for GOP now because we are more socially conservative and the Dems left us. It has nothing to do with Yankee migrations south which paled compared to the reverse until very recently...1980s on. Gingrich, Barr and Bush represent a few Yankee descended politicians not a migration wave.
If you can't see how the 3/5ths rule and more slave states would further diminish Yankee political power than I'm not sure how I can explain the obvious. Don't tell me you think they did all that because of Christian charity.