We’ve already got a “not Trump” candidate who is good enough for now.
That’s the issue. Is that really good enough to defeat Trump? For democracy being on the line, I think they really need to replace Biden. I think only Obama could convince Joe to step down. He would look Presidential and his legacy would be “fine”. If Biden stays in the race and loses to Trump, Biden’s legacy will be “his ego ended democracy”. The empire is collapsing.