I think the DNC will do whatever it takes to drag Joe Biden across the finish line as the party's nominee. They're not thrilled with him, but feel he's their best chance to retake the White House. If that were to happen, they know Biden is in no shape to last a full term. The person to watch is whoever they put in as Biden's running mate. That person is their real nominee.
Biden is dementing so rapidly that it is impossible to conceal.