Brent L. Top and Lawrence R. Flake, "'The Kingdom of God Will Roll On': Succession in the Presidency," Ensign, Aug. 1996, 22
Bruce McConkie said,
He is always the senior Apostle, the presiding Apostle, the presiding high priest, the presiding elder. He alone can give direction to all others, direction from which none is exempt.Bruce R. McConkie, "The Keys of the Kingdom" Ensign, May 1983, 21
Thus, the keys, though vested in all of the Twelve, are used by any one of them to a limited degree only, unless and until one of them attains that seniority which makes him the Lord’s anointed on earth.
Gordon B. Hinckley, "The Joseph Smith III Document and the Keys of the Kingdom," Ensign, May 1981, 20