Hubert Horatio Humphrey , Jr. ( May 27 , 1911 â `` January 13 , 1978 ) was the thirty-eighth Vice President of the United States , serving under President Lyndon B. Johnson . Hubert Horatio Humphrey , Jr. ( May 27 , 1911 - January 13 , 1978 ) , served under President Lyndon B. Johnson as the 38th Vice President of the United States .