With incumbent vice president Hannibal Hamlin remaining indifferent about the prospect of a second term in office, Andrew Johnson, the former senator from and current military governor of Tennessee, was named as Lincoln's vice presidential running-mate. He had been governor of Tennessee from 1853 to 1857 and was elected by the legislature to the Senate in 1857. In his congressional service, he sought passage of the Homestead Bill which was enacted soon after he left his Senate seat in 1862. When the Southern slave states, including Tennessee, seceded, he remained firmly with the Union. He was the only sitting senator from a Confederate state who did not resign his seat upon learning of his state's secession. In 1862, Lincoln appointed him as military governor of Tennessee after most of it had been retaken. In 1864, Johnson was a logical choice as running mate for Lincoln, who wished to send a message of national unity in his re-election campaign, especially to ensure the electoral votes of the border states.