Complex sentence: During his long political career, Cass served as a governor of the Michigan Territory, an American ambassador, a U.S. Senator representing Michigan, and was the nominee of the Democratic Party for President of the United States in 1848.
Split into simpler sentences: During his long political career, Cass served as a governor of the Michigan Territory, an American ambassador, and a U.S. Senator representing Michigan. He was the nominee of the Democratic Party for President of the United States in 1848.