Donald Trump can be seen as a combination of three demagogues we have witnessed in American history.
He is George Wallace (1919-1998), the Alabama Governor, who ran for President in 1968, and gained five states and 46 electoral votes, preaching racism and white supremacy. Fortunately, he was a third party candidate, and not a serious possibility to win the White House.
He is Joseph McCarthy (1908-1957), the Wisconsin Republican Senator, who promoted the Red Scare in the early 1950s, and had Roy Cohn as his chief aide. In later years, Roy Cohn was a friend and had an impact on young Donald Trump, and Trump now has a young aide, Stephen Miller, who is as nasty and mean spirited as Cohn was. Until McCarthy destroyed himself at the Army-McCarthy hearings in 1954, many saw him as a potential threat for the future, possibly even running for President.
He is also John C. Calhoun (1782-1850), the South Carolina Senator in the 19th century, who promoted secession, states rights, slavery, and white supremacy. As Vice President for nearly eight years under John Quincy Adams and Andrew Jackson, he was a heartbeat away from the Presidency. Although Calhoun died in 1850, many would later say that he helped to bring on the Civil War that began a decade after his death.