Complex sentence: He was an unsuccessful candidate for reelection in 1850 to the Thirty-second Congress, but he was elected to the Thirty-third Congress (March 4,1853-March 3,1855).
Split into simpler sentences: He was an unsuccessful candidate for reelection in 1850 to the Thirty-second Congress. Morrison was elected to the Thirty-third Congress (March 4,1853-March 3,1855).