FILE - This May 17, 1973 file photo shows Sen. Fred D. Thompson, Chief Minority Counsel of the Senate Watergate Committee, left, talking with Sen. Howard Baker, R-Tenn. during the Watergate hearings on Capitol Hill in Washington. . Baker, who asked what President Richard Nixon knew about Watergate, has died. He was 88. 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 U.S. ambassador to Japan during President George W. Bush's first term. (AP Photo, File)