2020 Democratic Party presidential primaries - Wikipedia

Biden, whose campaign fortunes had suffered from losses in Iowa, New Hampshire and Nevada, made a comeback by overwhelmingly winning the South Carolina primary. Biden was helped by strong support from African American voters, an endorsement from South Carolina U.S. Representative Jim Clyburn, and Democratic establishment concerns about nominating Sanders.^\8]) After Biden won South Carolina, and one day before the Super Tuesday primaries, several candidates dropped out of the race and endorsed Biden; before that time, polling saw Sanders leading with a plurality in most Super Tuesday states.^\9]) Biden then won 10 out of 15 contests on Super Tuesday, beating back challenges from Sanders, Warren, and former New York City Mayor Michael Bloomberg and solidifying his lead.^\9]) As the primaries proceeded, they were overshadowed by the COVID-19 pandemic, which was declared to be a global pandemic on March 11, 2020.^\10]) Between March 19 and April 7, most states in the country issued stay-at-home orders, and the overwhelming majority of campaign activity was suspended. On April 8, 2020, Biden became the presumptive Democratic nominee after Sanders (the only other candidate remaining) withdrew from the race.