Complex sentence: Wills was elected governor in 1940, succeeding Aiken, who chose to run for the United States Senate, and again in 1942, but chose not to seek a third term, citing poor health.
Split into simpler sentences: Wills was elected governor in 1940, succeeding Aiken, who chose to run for the United States Senate. He won again in 1942, but chose not to seek a third term, citing poor health.