As a member of the Virginia state legislature (1847–48; 1855) and as a states' rights Democratic governor (1849–52), Floyd opposed secession, but his growing belief in the Southern cause led him to resign in 1860 from the Cabinet post to which President James Buchanan had appointed him in 1857. At the same time, however, charges of financial irregularities in his office (never substantiated) prompted the president to request his resignation. With the outbreak of the Civil War (1861), he was appointed brigadier general by Confederate President Jefferson Davis. In 1862 he was in command of the Confederate forces at Fort Donelson in Tennessee but withdrew his brigade before the surrender, under circumstances never clarified. For this he was relieved of his command but was later made a major general of Virginia troops by the Virginia assembly.