How do you solve a problem like Joe Biden?

It is as though a giant trap has sprung: Democrats suddenly find themselves faced with the prospect of losing the White House and both houses of Congress just as the Supreme Court’s conservative majority has further empowered the presidency and hobbled the administrative state. Democrats’ scorn for Republicans at choosing an unpopular nominee for president, a candidate compromised by criminality and extremism, has turned to panic as they realise they may have committed to a nominee even more compromised in the eyes of voters, by infirmity. How did the party get itself into this mess? How can it fix things?