A Democrat, in 1964 he was elected to the U.S. House from the 2nd District after incumbent Republican Clifford McIntire ran unsuccessfully for the United States Senate, and he served from 1965 until 1973.

as a congressman Hathaway supported President Johnson's Great Society, he also helped lay groundwork to establish the Occupational Safety and Health Administration.

[1] In 1972 Hathaway ran for the United States Senate and defeated four-term Republican incumbent Margaret Chase Smith by 27,230 votes.

in 1973 Hathaway, received a letter from a woman complaining that she had been rejected by the United States Military Academy at West Point, N.Y., because she was female.

[2] Hathaway was an unsuccessful candidate for reelection in 1978, losing to his successor in the 2nd District, future Secretary of Defense William Cohen, by 84,967 votes.

[6] Hathaway was married to Mary Lee Bird of Horse Shoe, North Carolina, and Akron, Ohio, for over 61 years until her death, in 2007.