<Li> November 25--December 7, 1885, following the death of Vice President Thomas A. Hendricks, until John Sherman was elected president pro tempore . </Li> <P> When President Andrew Johnson, who had no vice president, was impeached and tried in 1868, Senate President pro tempore Benjamin Franklin Wade was next in line to the presidency . Wade's radicalism is thought by many historians to be a major reason why the Senate, which did not want to see Wade in the White House, acquitted Johnson . The President pro tempore and the Speaker of the House were removed from the presidential line of succession in 1886 . Both were restored to it in 1947, though this time with the president pro tempore following the speaker . </P> <P> William P. Frye served as President pro tempore from 1896 to 1911 (54th--62nd Congress), a tenure longer than anyone else . He resigned from the position due to ill health a couple of months before his death . Electing his successor proved difficult, as Senate Republicans, then in the majority, were split between progressive and conservative factions, each promoting its own candidate . Likewise, the Democrats proposed their own candidate . As a result of this three - way split, no individual received a majority vote . It took four months for a compromise solution to emerge: Democrat Augustus Bacon would serve for a single day, August 14, 1911, during the vice president's absence . Thereafter, Bacon and four Republicans--Charles Curtis, Jacob Gallinger, Henry Cabot Lodge, and Frank Brandegee--would alternate as president pro tempore for the remainder of the Congress . </P> <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>

The most powerful individual in the senate is the president pro tempore