How is slavery America orginal sin... but not Democrat Party orginal sin? ..."
Somewhere I saw it alleged that in 1860 some Delaware slaveholders voted for Republican Lincoln, but I can't confirm it, and if true, they were certainly the only slaveholders ever to do so.
And they would not be, strictly speaking, Republicans, since they voted for People's Party anti-Democrat candidates, who included only one Republican, Lincoln, on their ballots.
In 1860, throughout the South, the choice was basically, Breckenridge's Southern Democrats or John Bell's Constitutional Unionists, and both of those were slaveholders, the difference being Bell opposed secession and his supporters were able to keep eight Southern states from seceding before Fort Sumter, with four of those remaining in the Union even after Fort Sumter.
During the Civil War the Confederacy was ruled by the single-party Southern Democrats, which then remained in control of the "Solid South" for the next ~100 years.
Arguably, beginning in late December 1860, the Democrat Party officially declared secession and then war, against the United States, and I can find no historical record of where Democrats ever officially surrendered.
So far as I can tell, Democrats are still at war against the United States to this very day.
Democrats have always been deadly serious about their political goals.
Republicans, not always so much: