Second, to be more accurate about it, the brutal conquest of the south by the likes of 'pyromaniac' Sherman and his thugs combined with the the subsequent rape of the south by the carpetbaggers and thieir associates turned the south into solid Democrat for nearly a century.
Yes, but that doesn't entirely explain why the South decided to go with the Democrats. That part can then be explained by noting that the commander-in-chief during the war was a Republican. Had Abraham Lincoln been a Democrat, we would have seen the solid Republican South.
And sure, technically speaking Andrew Johnson was not a Republican, but he was on a ticket with Abraham Lincoln. I don't think many Southerners would have cared about anything else; that's enough association with the Republican Party for them right there.
Well, lets look at the two different aspects, first of how the war was fought and second how the south was treated after the war.
If the south had been defeated by the north following the generally accepted western rules of warfare (adhered to by McClellan and Lee) the level of animosity would have been far less than the practice of Sherman, Sheridan, Butler et al. who launched despicable attacks on civilians and their property.
Carl is correct, that there was a certain arrogance on the part of some Northern military men -- the contempt shown Southerners was, in some instances, remarkably offensive. Ben Butler may be a better example of this than Sherman, who is sometimes misunderstood. Sherman, like Grant, waged total war. However, as is pointed out in Mark Grimsley's, "The Hard Hand of War: Union Military Policy toward Southern Civilians, 1861-1865", the loss of civilian life at the hands of Sherman's men was almost nil.
Sherman DID destroy Southern railroads. He also destroyed subsistence stores that could have been used to feed local militia or guerillas. The theory, and it is a sound one, is that if you reduce the infrastructure in enemy territory, you reduce the ability and will to fight. Dropping the atomic bomb on Japan twice was hardly humane. But the lives lost, even among just the Japanese, would almost certainly have been greater had the U.S. proceeded with Operations Olympic and Cornet in 1946.
Most historians also reject the claim that Sherman ordered the burning of Columbia, South Carolina. This is simply untrue.
Unquestionably, crimes were committed against the South and its people throughout the Civil War. Remember that scene in "Glory", where the troops burned that farm? That happened. (This was not Sherman's command.) Such crimes are always inexcusable. And the Northerners who claim "lily white purity" and nobility for our side are intellectually dishonest.
But the other side of the coin is also worth a look. Southern troops could be, and sometimes were, horrendously brutal. The burning of Chambersburg, Pennsylvania was no accident. And unlike Columbia, S.C., the fire was order by the Confederate commander and set by his men.
My point is this: For every hell-hole like Camp Douglas or Elmira, there was Andersonville. For every massacre of unarmed Federal troops (as at Fort Pillow), there were brutal crimes committed against Rebels.
Each side must own its good history. And its bad.
But the overarching question -- what brought about Democratic dominence in the South for so long? -- is answered in the fact that for most people, perception is reality. Southerners were told and believed (and many still believe) that the Union Army was made up of murderous thugs, rapists and arsonists. And that Republicans, like old Abe Lincoln, were to blame for such crimes.
