Joe had a good run. He brought us out of the worst of the pandemic and set the economy on a decent trajectory. Now it's time for him to pass the baton to someone who'll put the final nail in the coffin of MAGA. I think it's the best decision he could make for his legacy and the good of the country.
Now it is on the Dems to choose someone who is electable. I'm not too confident about Kamala but shes the most likely person to replace him.
There's no one who can replace him. If he drops out, Trump is guaranteed to win - full stop.