Byrd was fourth person in the state ( as President pro tempore of the Senate , usually longest serving Senator from majority party ) from January 1989 to January 1995 , from January 3 , 2001 to January 20 , 2001 and again from June 2001 to January 2003 and January 2007 until his death in 2010 . After Republicans retook control of the Senate , he became the honorary President `` pro tempore emeritus '' In 2007 , Byrd became President Pro Tempore of the Senate again . From 1989 to 2010 he served as the President pro tempore of the United States Senate when the Democratic Party had a majority , and as President pro tempore emeritus during periods of Republican majority beginning in 2001 .