<P> In January 1945, the 79th Congress elected Kenneth McKellar, who at the time was the Senator with the longest continuous service, to be President pro tempore . Since then, it has become customary for the majority party's senior member to hold this position . Arthur Vandenberg (in 1947--1949) was the last president pro tempore not to be the senior member of the majority party, aside from the single day accorded Milton Young (in December 1980), who was the retiring senior member of the Republican Party, which would hold the majority in the incoming 97th Congress . </P> <P> Three presidents pro tempore subsequently became Vice President: John Tyler, William R. King and Charles Curtis . Tyler is the only one to become president (in April 1841, following the death of William Henry Harrison). </P> <P> While the president pro tempore does have other official duties, the holders of the office have, like the vice president, over time ceased presiding over the Senate on a daily basis, owing to the mundane and ceremonial nature of the position . Furthermore, as the president pro tempore is now usually the most senior senator of the majority party, he or she most likely also chairs a major Senate committee and has other significant demands on his or her time . Therefore, the president pro tempore has less time now than in the past to preside daily over the Senate . Instead, junior senators from the majority party are designated acting president pro tempore to preside over the Senate . This allows junior senators to learn proper parliamentary procedure . The acting president pro tempore is usually reappointed daily by the president pro tempore . </P> <P> In June 1963, because of the illness of president pro tempore Carl Hayden, Senator Lee Metcalf was designated permanent acting president pro tempore . No term was imposed on this designation, so Metcalf retained it until he died in office in 1978 . </P>

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