In 1839, he sought to regain his seat, initially as a Whig, but when another candidate sought the Whig nomination, he ran as a Democrat and was elected. From that time he supported the Democratic party and built a powerful political machine in Greene County.[29][30] Johnson became a strong advocate of the Democratic Party, noted for his oratory, and in an era when public speaking both informed the public and entertained it, people flocked to hear him.[31]
In 1840, Johnson was selected as a presidential elector for Tennessee, giving him more statewide publicity. Although Democratic President Martin Van Buren was defeated by former Ohio senator William Henry Harrison, Johnson was instrumental in keeping Greene County in the Democratic column.[32] He was elected to the Tennessee Senate in 1841, where he served a two-year term.[33] He had achieved financial success in his tailoring business, but sold it to concentrate on politics. He had also acquired additional real estate, including a larger home and a farm (where his mother and stepfather took residence), and among his assets numbered eight or nine slaves.