Biden 22%
Harris 20%
Warren 14%
Sanders 13%
Buttigeig 4%
It looks like debates have consequences. When you add Sanders in the Iowa Suffolk poll at 9% things are not looking good for him either. Age may also matter more than policy.
Nate Siver commenting on the Iowa poll
"Among voters who *aren't* backing Biden in Iowa, the top reason isn't ideology but *age*. Note that several of these responses refer to age (e.g. "pass the torch"), not just the top one".