When Garibaldi conquered the Two Sicilies in 1860 he set up a republican government with himself as dictator (in the old sense of the word), and was originally interested in keeping it as an independent state for iirc a year or more to allow proper republican institutions time to lay down their foundations. It was only that his Italian nationalist sentiment was stronger than his republicanism that led to him handing over everything to the Savoyards. Have him change his mind, or have him die and have one of his more die-hard republican lieutenants take charge. Now you have a three-sided conflict between the monarchist north, republican south, and the French-backed Papacy in the center.