Lewis Cass (October 9, 1782 – June 17, 1866) was an American military officer and politician. During his long political career, Cass served as a governor of the Michigan Territory, an American ambassador, a U.S. Senator representing Michigan, and co-founder as well as first Masonic Grand Master of the Grand Lodge of Michigan. He was the losing nominee of the Democratic Party for president in 1848. Cass was nationally famous as a leading spokesman for the controversial Doctrine of Popular Sovereignty, which would have allowed voters in the territories to determine whether to make slavery legal instead of having Congress decide.