Last week was Joe Biden's worst week of the campaign, besides the day he realized he got the nomination and was in trouble now. Seriously, for a guy who is trying to prove he is not in cognitive decline, my dude sure said a lot of crazy poop last week (see JOE BIDEN JUST ASKED A BLACK REPORTER IF HE DOES COCAINE. NO, REALLY. and THE GOP JUST RELEASED A 46 MINUTE VIDEO OF JOE BIDEN TALKING NONSENSE). Democrats had 217 candidates to choose from, and they chose a guy who is lucky he remembers his pants, let alone remembers he used to be vice president.
Dems have no one to blame but themselves, because even when still had his wits about him (barely), Biden would randomly spit out things that didn't make sense, as this resurfaced Robin Williams bit points out.