Robert Blackford Duncan was an American politician from the state of Oregon. A Democrat, he served multiple terms in the Oregon Legislative Assembly and as a U.S. congressman from Oregon. In the Oregon House of Representatives he served as speaker for four years, and in the U.S. House he represented two different districts. The Illinois native and World War II veteran ran three unsuccessful campaigns to be elected to the U.S. Senate.

The 1968 United States Senate election in Oregon was held on November 5, 1968. Incumbent Democratic U.S. Senator Wayne Morse was seeking a fifth term, but narrowly lost re-election to 36 year-old Republican State Representative Bob Packwood in a very close race.