Earmark it.

Here is how the process works to get a Dem candidate on the ballot. The candidates campaign in the states. The states hold primary elections. The winning candidate in each state gets those electors at the national convention.
Remember, the Democrats kept RFK jr from running in any state primary. At this point Biden is the only candidate with electors going to the national convention. There is no other candidate coming out of the Democrat national convention that will be the nominee.

Biden will be the nominee.

BUT……

There is a short window after the convention and before the 60 day period before the national election. If the nominee dies or steps down before that window closes, the DNC can - behind closed doors – select a replacement candidate.

That might be a bet to make.

You never heard of a convention floor fight.

That already happened when the Dems said Biden is the the candidate and kept RFK jr from running in the primaries.
Barry wants a fourth term.