Complex sentence: He was also a delegate to the 1956 convention in Chicago, which renominated former Governor Adlai E. Stevenson of Illinois, once again to challenge Republican presidential nominee Dwight David Eisenhower.
Split into simpler sentences: He was also a delegate to the 1956 convention, also held in Chicago. The delegates renominated former Governor Adlai E. Stevenson of Illinois, once again to challenge Republican presidential nominee Dwight David Eisenhower.