Davis was an inspector and deputy collector of customs in Laredo before being appointed district attorney in Brownsville. After refusing to take the oath of loyalty to the Confederacy as a district judge, his judgeship was vacated.

Davis joined First Texas, a Union cavalry regiment, and was captured in Matamoros while trying to cross into Mexico with his family. As president of the Constitutional Convention he supported restricting political rights of secessionists and expanding rights for blacks.

Davis was elected governor in a close race with Andrew J. Hamilton. He supported a state police, protection of the frontier, public schools and bureaus of immigration and geology. Davis was defeated by Richard Coke in 1873, ran again in 1880, but was defeated by Oran Roberts. He ran for Congress, again unsuccessfully, and was nominated in 1880 as customs collector at Galveston but refused the position. Supporters hoped for an appointment from President Chester A. Arthur, but one did not come.