I can understand why did FDR have a big margin. He won a national landslide, there was the anti-Lincoln's party vote in the South, the southeners were willing to vote for democrats even if they were northern liberals, many southeners were very poor and the New Deal was good for them.
But how is it possible to explain 97%?
https://en.wikipedia.org/wiki/1936_United_States_presidential_election_in_Mississippihttps://en.wikipedia.org/wiki/1936_United_States_presidential_election_in_South_CarolinaIn 1 county in Mississippi and in 2 counties in South Carolina, FDR had 100%
Usually, it's not easy to find 97% who have the same opinion living in a place. It's hard to find this percentage in a single county in the most recent elections.
