In all of recorded history — at least as I know it — every time the Democratic Party has chosen a presidential candidate who was a former vice president, they have lost:
1968 Hubert Humphrey
1984 Walter Mondale
2000 Al Gore
2020 Joe Biden
Every time the Democratic Party has chosen a presidential candidate who was an experienced, established, and familiar politician, they have lost:
1952 Adlai Stevenson
1956 Adlai Stevenson
1972 George McGovern
1988 George Dukakis
2004 John Kerry
2016 Hillary Clinton
2020 Bernie Sanders
Only when the Democratic Party chooses a presidential candidate who is charismatic, inexperienced, and unknown before the campaign, do they win:
1960 John Kennedy
1976 Jimmy Carter
1992 Bill Clinton
2008 Barack Obama
2020 Pete Boot-a-judge