There is still a primary, but the incumbent has only lost his party’s nomination 4 times, only Democrat Franklin Pierce in 1856 was elected the other 3 ascended from Vice President. It has never happened since the modern primary system was created in the 1970s.
Not voting for Biden in the primaries is perfectly fine.
There are primaries for Dems? I thought Biden was automatically the candidate as current POTUS.
There is a whole calendar
https://ballotpedia.org/Changes_to_the_2024_Democratic_presidential_primary_calendar
There is still a primary, but the incumbent has only lost his party’s nomination 4 times, only Democrat Franklin Pierce in 1856 was elected the other 3 ascended from Vice President. It has never happened since the modern primary system was created in the 1970s.