U.S. President Donald Trump and Democratic presidential nominee Joe Biden participate in their first 2020 presidential campaign debate held on the campus of the Cleveland Clinic at Case Western Reserve University in Cleveland, Ohio, U.S., September 29, 2020. REUTERS/Brian Snyder
US President Donald Trump and Democratic presidential nominee Joe Biden took part in a highly fractious first debate last month. Reuters

US election: the roots of a dirty 2020 campaign stretch deep into American political history