Robert A. Toombs, Senator from Georgia, perhaps the #1 fire-eater in the US Senate. Openly favored full restoration of the Slave Trade. Actually, legalization since slave ships were arriving in the South till Lee surrendered. OTL, he tried for the job of POTCSA but was beaten out by Davis. He had to settle for being Davis' first Secretary of State. Stephens, his fellow Georgian, got the VP. No Davis? Pathway is open for Toombs, who was an outstanding orator in his day. No Lincoln, but who was? He may well have been able to rally the Confederate nation in a way Davis never could. He might have presented to the Southern people a civilian leader for them to look up to, rather than a military man like Robert E. Lee.
But all this comes at a price. Even by the standards of the Confederacy, Toombs was a fire-eaters' fire-eater. As President of the Confederacy, his personal politics would have frozen the British Empire into strictest neutrality. Napoleon III wouldn't care, but no way does he break the blockade without Britain.
In the end? A more united South, but Lincoln's diplomacy becomes a whole lot easier.