An FBI referral recommending indictment should be enough to derail Hillary. So the ball is not entirely in the AG's court on this one.
That would be dicey, I suppose. I've read that they have put 100 agents on the case full time. Even if that happens, she claims to be an innocent victim. She gets sympathy. It's all about gaining delegates. Sure, maybe the big donors get scared off, and maybe a few of the unpledged PLEO to the DNC think tice, but a number of them were somehow put off by Sanders' legislative agenda to begin with, and those are really the only two viable candidates. I guess and indictment might cause a hasty recruitment of Kerry or Biden or someone like that, but it would all look very silly, and it still comes down to a fight between Clinton and Sanders.
I'm sure I wouldn't want to be in Obama's justice department if an indictment request comes to them. That's a lose-lose situation for them, and I'm sure that they'll do their best to delay any decision for as long as possible if the FBI does recommend an indictment. I know I would in their shoes.
I say leave it to the voters. I don't trust Hillary Clinton at all, and in fact I loathe her brand of cynicism and exploitation--I certainly can't imagine ever voting for her--but if a plurality of my fellow Americans want her to be president, then we should get what we deserve. Anyway, an indictment doesn't bar someone from being president, unless I misunderstand the presumption of innocence.