He was born and raised in Esmond, North Dakota. He was a veteran of World War II. Hoffner served as a Democrat in three separate stints in the House of Representatives: from 1962 to 1966, 1968 to 1972 and 1983 to 1984 in addition to serving as the House's minority leader in the 1971 session. During his eight years in the Senate from 1972 to 1980, he was its minority leader from 1975 to 1980.