In 1968, Duncan came back to challenge Senator Morse in the Democratic Senate primary. Again, Duncan's war views played a role. 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. Morse went on to narrowly lose in the general election to Republican state Representative Bob Packwood, who favored continued funding of the war.