Following the war, Abbott remained in North Carolina. He was active in state politics, serving as a delegate to the State constitutional convention in 1868. During this time, his political strength came primarily through the black population. He believed in their capacity and assisted in organization and politically counseling them in ways which brought him blunt warnings from the white population. He was elected to the United States Senate that same year, representing North Carolina in that body for the first time since July 1861, when the state's two senators were expelled following the North Carolina's secession from the Union. He served as a Senator from July 14, 1868 to March 4, 1871.