that would eventually become the Kansas–Nebraska Act. To gain the support of Southern senators, the bill contained an amendment that repealed part of the Missouri Compromise to allow slavery north of the 36°30' parallel. Bell opposed this amendment, warning that a repeal of the Missouri Compromise would lead to endless sectional strife. He was assailed by Southern senators for this stance, and was blasted on the Senate floor by Robert Toombs of Georgia. Bell was one of just two Southern senators (the other being Sam Houston) to vote against the final bill. The division between Northern and Southern Whigs over the Kansas-Nebraska Act doomed the party, with Northern Whigs shifting to the new Republican Party. In early September 1856, he was selected to be a delegate to the 1856 National Whig Convention. The convention nominated former president Millard Fillmore, who had already been nominated by the American Party, or "Know Nothings." While he campaigned for Know Nothing candidates, Bell did not endorse many of the party's more controversial positions, such as its anti-Catholic stance. Various newspapers, including Brownlow's Knoxville Whig, the New Orleans Delta, and the St. Louis Intelligencer, endorsed Bell as the American Party's presidential candidate, but the party's nomination went to Millard Fillmore. In 1857, Democrats regained control of the Tennessee state legislature. They elected Andrew Johnson to fill the expiring term of Senator James C. Jones. Although Bell's term didn't expire for another two years, the legislature was so disgusted with him that they went ahead and chose his replacement (Alfred O. P. Nicholson) and demanded that he resign. He was continuously attacked by other Southern senators. In late 1857, he threatened to challenge Robert Toombs to a duel after Toombs called him an abolitionist, but Toombs retracted the statement. In February 1858, Bell and Johnson were involved in a heated altercation on the Senate floor after Johnson questioned Bell's loyalty to the South. In March 1858, Bell was one of just two Southern senators (the other being John J. Crittenden) to vote against the admission of Kansas under the Lecompton Constitution, ignoring orders from the Tennessee state legislature to vote for it. In his last session in the Senate in 1859, Bell voted against an attempt to purchase Cuba from Spain, opposed the Homestead bill, and voted in favor of subsidies for the Pacific Railroad. Presidential candidacy Annoyed by the continuous sectional strife in the Senate,