Lyman Trumbull (1813-1896) was a Republican Senator (originally a Democrat) from Illinois who helped lead the Liberal Republican Party in 1872. He then returned to being a Democrat.
Trumbull avidly supported the Lincoln administration and endorsed the radical Republicans on their Reconstruction measures. Yet he would not support the movement to remove the president from office, and was one of a handful of senators who voted against the resolution. He was co-counsel for Tilden in the contested Hayes-Tilden election of 1876.