Succession to the presidency of the Church of Jesus Christ of Latter-day Saints follows a distinctive rule: on the death of a President, the First Presidency is dissolved and the Quorum of the Twelve Apostles governs the Church collectively until a new President is set apart, almost invariably the apostle who has served longest in the Quorum, regardless of age. The senior apostle then chooses two counselors, and the reconstituted First Presidency is presented to the general membership for a sustaining vote at a solemn assembly, a ritual affirmation rather than a contested election.
This seniority convention was not written into scripture but emerged from the chaotic 1844 succession crisis after Joseph Smith's death, when several men, including Sidney Rigdon and James Strang, claimed the right to lead. Brigham Young, then president of the Quorum of the Twelve, argued that the apostles collectively held the keys Smith had conferred on them and that leadership therefore passed to the Quorum as a body; the majority of the Nauvoo membership accepted this reasoning, and Young was sustained as President in 1847. The precedent held for every subsequent transition.
Because seniority rather than election determines the choice, Presidents have often been elderly at the time of their sustaining, and the office has sometimes passed through a rapid sequence of short tenures when several senior apostles died within a few years of one another.