The Illinois native and World War II veteran ran three unsuccessful campaigns to be elected to the U.S. Senate.

His mother, Catherine Blackford, was of Welsh origin—her parents had immigrated from Wales to the United States in the late 19th century.

[1] In college he met fellow student Marijane Beverly Dill (born June 30, 1920) and the two were married on December 19, 1942.

[1] In 1948, Duncan received his LL.B from the University of Michigan Law School and passed the bar in October of that year.

[1] While Duncan strongly supported President Johnson's Vietnam War policies, his Republican opponent, Governor Mark Hatfield, was an outspoken critic.

[3] The differences between Duncan and Hatfield on the war would produce one of the great splits in the modern Oregon Democratic Party.

Though Duncan was initially far ahead of the anti-war maverick Morse, Morse closed the gap at the end and won a narrow victory, aided by the beginning of the Paris Peace Accords, which brought the possibility of the end of the war.

[8] Morse went on to narrowly lose in the general election to Republican state Representative Bob Packwood, who favored continued funding of the war.

After Edith Green retired from Congress, Duncan ran for her Portland-based seat from Oregon's 3rd congressional district in 1974 and returned to the House.