2016 Sanders got a lot of support based on not being Hillary Clinton.
As for support: (from Quinnipiac)
DEBATE Q6............ ATTN TO PRES CAMPAIGN Q1
Paid Little/
Watch Attn No Attn A lot Some None
Biden 18% 29% 17% 21% 27% 18%
Sanders 8 13 24 10 14 22
Of those who paid "no attention" to the debate at all, 24% support sanders. Of those paying "no" attention to the presidential campaign, 22% support sanders.
This is inexplicably WORSE than Biden's numbers (17% and 18%, respectively).
Of those who watched the debate, sanders comes in fourth at 8%, well behind Harris, Warren, and Biden and barely above Pete at 6%. Of those who pay "a lot" of attention to the presidential campaign, Sanders is again a distant fourth at 10%.
Sanders is coasting on name recognition from 2016 and little else. The more attention one pays to the race, the less likely they are to support Sanders. Without those not paying any attention to anything, he'd be in the basement with Booker and O'rourke.