Lewis Cass (October 9, 1782June 17, 1866) was an American military officer, politician, and statesman. He represented Michigan in the United States Senate. He was in the Cabinets of two U.S. Presidents, Andrew Jackson and James Buchanan. He was also the 1848 Democratic presidential nominee. He was an important person for the idea of Popular Sovereignty. That idea said that the people in each territory should decide whether to allow slavery.