No he hasn't failed.
Again, he's up in the polls. It's Trump that needs the votes, needs the viewing figures and needs to sway voters.
The absolute best case scenario for him from last night's shit show was that nobody was swayed either way.
That's bad for him, good for Biden. All Biden had to do was still be standing strong in the polls after 90 minutes and he is.
Plus, the next two debates will see a drastic drop in viewing figures which is an absolute nightmare for Trump and his campaign yet it's his own doing.
In no way, shape or form did Biden fail last night, he just kept the ball in the corner when he could while Trump hoofed it up the pitch every time.