 Mitchell was elected from the sixth district of Maryland to the Eighteenth and Nineteenth Congresses, and served from March 4, 1823 to March 3, 1827.He was not a candidate for renomination in 1826, and was an unsuccessful candidate for the governorship in 1829.He was elected from the sixth district as a Jacksonian to the Twenty-first and Twenty-second Congresses and served from December 7, 1829, until his death in Washington, D.C..