After having his civil rights restored following the war, Lamar returned to the U.S. House of Representatives in 1873, the first Democrat from Mississippi to be elected to the House since the Civil War. He served there until 1877. Lamar was elected by the state legislature (as was the practice at the time) to represent Mississippi in the U.S. Senate from 1877 to 1885. Lamar was a staunch opponent of Reconstruction, and did not consider freedmen and other black Americans fit to vote. He promoted "the supremacy of the unconquered and unconquerable Saxon race."