Complex sentence: That same year, he was elected as a State Senator, where he became senate president "pro tempore" of a Legislature that included 42 representatives of African-American descent (half of the chamber, and seven of 36 seats in the Senate).
Split into simpler sentences: That same year, he was elected as a State Senator. He became senate president "pro tempore" of a Legislature that included 42 representatives of African-American descent (half of the House, and seven of 36 seats in the Senate).