Johnson helped organize a mechanics' (working men's) ticket in the 1829 Greeneville municipal election. He was elected town alderman, along with his friends Blackston McDannel and Mordecai Lincoln. Following the 1831 Nat Turner slave rebellion, a state convention was called to pass a new constitution, including provisions to disenfranchise free people of color. The convention also wanted to reform real estate tax rates, and provide ways of funding improvements to Tennessee's infrastructure. The constitution was submitted for a public vote, and Johnson spoke widely for its adoption; the successful campaign provided him with statewide exposure. On January 4, 1834, his fellow aldermen elected him mayor of Greeneville.