That happens if Biden slips and falls in the bath tube, too. Its not an argument for keeping him at the top of the ticket.
No that is not what happens. I’m not arguing to keep him at the top of the ticket. Exactly the opposite: I’m arguing to drop him from the not yet official ticket, but for him to stay on as president until his term ends. That keeps Johnson still only second-in-line for the presidency, with Harris still first-in-line.
If Biden (referring to his governmental role as the current President) dies, Vice President Kamala Harris immediately becomes President.
Whereas referring to his nongovernmental role once (IF) he becomes the official nominee of the Democratic Party, nobody is automatically elevated to be the new nominee of the party. If it’s before the election, the executive board of the DNC determines the new nominee. Harris would very likely become the official nominee, but that’s not their only choice.
But Biden is not yet the official nominee no matter how many times he and his supporters say he is. He is only the presumptive nominee. So if he died, was incapacitated, or dropped out as a candidate for the nomination now, before the convention roll call, it becomes essentially an open convention and the nominee is chosen the way it used to be, by the convention. Which might take multiple roll calls, behind the scenes favors trading, and all sorts of “fun” drama.
In none of those cases is Speaker of the House Johnson elevated to anything.