 In 1838, he served as the solicitor general for Georgia's Cherokee circuit

In 1840, Lumpkin unsuccessfully ran for the United States House of Representatives; however, he ran again in 1842 and won election as a Democrat to the 28th United States Congress.He was elected to two additional terms and served from March 4, 1843, until March 3, 1849.From 1850 through 1853, Lumpkin served as a superior court judge in Georgia's Rome circuit.