Complex sentence: Mahone led the successful effort to elect the Readjuster candidate William E. Cameron as the next governor, and he himself was elected to served as a Senator in the U.S. Congress from 1881 to 1887, when he lost his seat to Democrat John W. Daniel.
Split into simpler sentences: Mahone led the successful effort to elect the Readjuster candidate William E. Cameron as the governor. Mahone was elected as a US Senator from 1881 to 1887, when he lost his seat to Democrat John W. Daniel.