David Rice Atchinson was a United States Senator from Missouri and for a time President prop tempore of the Senate. He supported slavery apologetically, and supported the annexation of Texas as a slave state and abolition of that portion of the Missouri Compromise which prohibited slavery in the territories above the Missouri line. Rather, he proposed that the slavery issue be settled by popular sovereignty. He encouraged Stephen Douglas of Illinois to introduce the Bill into the Senate which later became the Kansas-Nebraska Act.
Atchinson fought briefly on the Confederate side in the Civil War as a general in the Missouri State Guard; however after Union forces gained control of Missouri in 1862, he resigned his commission and retired to his farm.
Among the more interesting aspects of his political career is that he claimed to be President of the United States for one day. The term of James K. Polk as President expired at noon on March 4, 1849, a Sunday. His successor, Zachary Taylor, refused to be inaugurated on a Sunday; and Taylor's Vice President elect, Milliard Fillmore was also not inaugurated. Under the then Presidential succession act, Atchinson, as Senate president pro tempore, became Acting Vice President; and in the eyes of some, President of the United States, albeit for only one day. Taylor was inaugurated on Monday, March 5.