US Senate Lamar Alexander confirmed Baker's death in a news release today.
Baker, a Republican, served 18 years in the Senate. He earned the respect of Republicans and Democrats alike and rose to the post of majority leader. He served as White House chief of staff at the end of the Reagan administration and was US ambassador to Japan during President George W Bush's first term.
His question at the 1973 Senate Watergate hearings, 'What did the president know and when did he know it?' became famous. It instantly focused the nation's attention on the cover-up that more than the Watergate building break-in itself eventually brought down Nixon's presidency.