Complex sentence: He was then elected Governor of Mississippi in 1819, serving from 1820 to 1822 and was an unsuccessful candidate for the U.S. House of Representatives in 1820 to the Seventeenth Congress and in 1822 to the Eighteenth Congress.
Split into simpler sentences: He was then elected Governor of Mississippi in 1819, serving from 1820 to 1822. Poindexter was an unsuccessful candidate for the U.S. House of Representatives in 1820 to the Seventeenth Congress and in 1822 to the Eighteenth Congress.