List all major candidates of the Democratic Party who are or were running for Presidential election in 2020 according to the Wikipedia page.
A major candidate has either:
(a) held public office;
(b) been included in a minimum of five independent national polls; or
(c) received substantial media coverage.
Nice quiz! I just posted a similar one that is a little more up to date (September 2019) and includes major republican challengers if you want to check it out!