William Morgan Cassidy (born September 28, 1957) is an American gastroenterologist and politician who is the senior United States Senator from Louisiana, serving since 2015.
A member of the Republican Party, he previously served as a member of the U.S.
House of Representatives and the Louisiana State Senate.
Born in Highland Park, Illinois, Cassidy is a graduate of Louisiana State University and LSU School of Medicine.
In 2006, he was elected a member of the Louisiana State Senate for the 16th district, which included parts of Baton Rouge.
In 2008, he was elected to the U.S.
House of Representatives, defeating Democratic incumbent Don Cazayoux.
In 2014, Cassidy defeated Democratic incumbent Mary Landrieu to represent Louisiana in the U.S.
Senate, becoming the first Republican to hold the seat since Reconstruction.