215th Pope of the Catholic Church. Pontificate 1503 - 1503 (26 days). This selection of Pius III to papacy was said to be a compromise between factions, Borgia and della Rovere, picking a frail cardinal with long experience. After a brief pontificate of twenty-six days he died of an ulcer in the leg, or, as some have alleged, of poison administered at the instigation of Pandolfo Petrucci, governor of Siena.