I understand the line, it does not reflect reality.
Well, you clearly don't, because OP's whole contention was if the candidate was anyone else but Trump, and yet here you are continuing to argue something the OP isn't disputing.
2016: "When they go low, we go high."
Armchair redditor: Why are Dems fighting with their hands cuffed behind their backs?
2024: "Okay, we'll take one off."
Armchair redditor-turned-lemming: "No, not like that!"
And Biden and Trump should both in theory put out a “I’m fine but if I develop dementia during the next turn this is the plan” plan. For Biden, that will help a lot of people who are on the fence between him and nobody see him as a better candidate and turn out in higher percentages.
I believe that's called a running mate, and not too many people are keen on a President Harris.
I came to the same conclusion in a post on a sub that was debating whether or not they should re-open permanently or not. You can obviously imagine how well it went over.
People will look for anything they can find in order to defend crossing their own picket line.