Joe Biden may have earned Bernie Sanders’s endorsement months before Hillary Clinton did in 2016, but the former rival’s voters aren’t necessarily sold on his campaign just yet.

The warning signs have been flashing for some time, with the presumptive 2020 Democratic nominee and former vice president never managing to crack low double-digit support among young people in this year’s primary contests. That didn’t matter when it came to winning most Super Tuesday states, where the field was split enough to allow Biden to cruise to victory easily.