@jack wow, what a great question this is 
“If Joe Biden doesn't have the cognitive function to run for re-election, then he certainly doesn't have the cognitive function to remain as Commander-In-Chief. 

How can any Dem pushing him to drop out of the presidential race, argue in good faith that he should stay on as POTUS?”

-JD Vance 

 

 The problem is that Kamala Harris isn't senile, but is as dumb and radical as someone who is.  President Harris would be worse than a senile President Biden, so they are limping along till the election hoping those behind Biden can keep it together for a few more months. 

 That’s certainly a plausible scenario,, maybe a box of rocks is why they need to run for them ..