Both my hope and my suspicion is we’re into something similar to the Bradley Effect, where black LA mayor Tom Bradley ran for CA guv. He was heavily favored to when, but all pollster were shocked when he lost.
I’m betting folks just don’t want to publicly admit they’re not voting for HRC.
Polls are likely using 2008 or 2012 turnout numbers for this election. That cannot work. The enthusiasm for Hillary is simply not there.