The really nonsensical part about the OP's question is that one party doesn't win "the election" in the U.S.: we can (and do) have divided government. It's actually quite likely that this year's election will see democrats regain the senate but republicans keep the house, resulting in both parties winning and losing in different races.
In the OP's defense, the thread specifically asks which party will win the presidential election.
I know a couple Sanders-holdouts who are self-identified democrats. Or, rather, they were Sanders-holdouts last I checked with them, which was prior to yesterday's announcement from Sanders that he will be voting for Clinton.
As announcements go, not earth-shattering. He's been signaling support for Clinton for months, now. I'm actually surprised we didn't see a full-on endorsement last week. I'm sure that too will come, soon enough.