My answer in the Obama '12/Trump thread is more applicable here (although the voter defined here would be a subset of that defined in the other thread.
A normally reliable Democratic voter for whom the issue of Hillary's e-mails (not Benghazi, as such a voter would likely have voted for Romney) is just too much.
Not that I am such a person (I'm still with her), but I can certainly see that happening. Many workplaces might be more hostile to her than to Obama ("If I did what she did, I'd probably be taken to some secret prison [substitute Gauntanamo Bay]"), and that could rub off on people.
