Seaver was elected as a Democratic-Republican to the Eighth and to the four succeeding Congresses (March 4, 1803 – March 3, 1813). He was one of six Democratic-Republican representatives to oppose the Twelfth Amendment to the United States Constitution.[1] Seaver was an unsuccessful candidate for reelection in 1812 to the Thirteenth Congress. He served as member of the State constitutional convention in 1820. He was again a member of the State house of representatives in 1822, 1823, and 1826. He died in Roxbury, Massachusetts, March 1, 1844.