In 1833, Col. Smith was elected to the State Senate, serving six years. In 1849 President Tyler appointed him United States District Attorney for the District west of the Blue Ridge, which position he held until the close of that Administration. In 1855, he represented Kanawha county in the General Assembly, under the Constitution of 1850, in the Convention to frame which he was an active member. He was a Whig in sentiment, and in 1861, President Lincoln made him District Attorney, in which office he served, under the old and new State, until 1868, when he resigned. He was a member of the Convention to frame a Constitution for West Virginia. He was a Democratic candidate for Governor in 1866, and was defeated. In 1870, he was one of Kanawha county's delegates in the Legislature. He died at his home in Charleston, December 10, 1887. Up to within a short time of his death he was remarkably hale and vigorous for one of his advanced age.

Col. Smith was one of the finest specimens of physical manhood ever in his section of the State, and of mental clearness and forcible impress contemporary only with George W. Summers, the orator of Western Virginia. He was one of the greatest lawyers Virginia ever produced; not eloquent, attractive or polished, but able, massive, powerful, irresistible. On account of his great legal learning, he will not soon be forgotten.