"Brain melt"
Yes, he did seriously lose the plot there, it's true!
Because of the topic, I started noticing the two commentators in that clip, and they also had the occasional pauses to find the necessary words. The guy got over it by referring to everything as "sh*t" and every person as "motherf*cker". The girl did better, imo, though I heard, "..It's very I mean It's painful..." and "..but sometimes you know but sometimes..." It's very difficult to talk without that kind of stuff happening.
I liked the point they made though, that "Grandad" Biden was still the voters' choice.