Complex sentence: A Democrat, he won a record four elections and dominated his party for many years as a central figure in world events during the mid- 20th century, leading the United States during a time of worldwide economic depression and total war.
Split into simpler sentences: A Democrat, he won a record four elections and dominated his party. He was a central figure in world events during the mid- 20th century, leading the United States during a time of worldwide economic depression and total war.