Randolph B. Campbell, "Houston, Sam," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-00528.html.
The Texas legislature elected Houston to the U.S. Senate on 21 February 1846. He drew a two-year term upon entering the Senate but was elected to a full term in December 1847. As sectional animosity over slavery increased, Houston took what would become an unalterable stance against extremism and in defense of the Union. Houston's moderate views on slavery supported his determination to preserve the Union. He owned slaves throughout his life and did not see the institution as a compelling moral issue; he defended it as a practical necessity, a way of providing labor and race control, and rejected the more aggressive view associated with John C. Calhoun and other extremists that slavery was a "positive good." Time would deal with the institution, he hoped, if fanatics would leave it alone. He voted in 1848 for organizing the Oregon Territory with a prohibition on slavery, and he refused to sign John C. Calhoun's 1849 "Southern Address," which called for sectional unity in defense of southern rights. He voted for all parts of the Compromise of 1850. Houston was elected to a third term in the Senate in January 1853, but his unionism began to injure his political career seriously in 1854 when he voted against the Kansas-Nebraska Act. Many of his constituents never forgave what they regarded as an antisouthern act. In 1855 the state legislature officially condemned his vote and indicated that he would not be reelected when his term expired in 1859. Houston identified with the Know-Nothing party in 1855-1856 and ran for governor of Texas in 1857. In that contest he suffered the only electoral defeat of his career, losing to Hardin R. Runnels, an ultrasoutherner.