It is indeed a fact, but it’s also solid conjecture that something changed c. 1900 wherein Democrats became more about “Progressivism” (socialism) while Republicans less so. (Teddy Roosevelt left the Republican party declaring himself “Progressive” - which I doubt any prominent Republicans had done SINCE.) They flipped basically. Also consider Dems UNIVERSALLY celebrate the US ONLY when it comes to the “Civil War” - they are lock-step pro-Union and Lincoln; otherwise they hate the US, while this is not true of the average “Southerner” today. Republicans as usual are more “open-minded” on this and many of us do not sympathize much with Lincoln and the “Union”.
Other than wasting huge amounts of money, empowering the feds the New Deal achieved nothing. So much so that in 1938 , at the height of it all then Secretary of The Treasury commented that "We're spending money but gaining nothing''. The worst effects of the Depression had begun to lessen by 1939 but undeniably America's entry into WW2 ended it for good. As to socialism in the Democrat Party most credit that with George McGovern's failed 1972 bid for The White House. Yes I know how the Dems latch on to The Civil War, pro- Union and Lincoln, yes it's true and their hatred of the US knows no bounds. Today the Democrats new private army is BLM and Antifa. And it's some what disappointing to read that , again for someone, that is you, who appears at times to have support for the Confederacy to have resentment for Lincoln and the Union which the South rejoined. What is with Lost Causers and the fact they won't admit they're really closet Democrats?