What happens if they find her guilty after she is elected?
If it's before she takes office, Obama could pardon her. Would be a smear on the end of his legacy but might a Nixon/Ford style situation to take the personal hit and move the country forward.
If it's after she takes office, most likely impeachment or resignation. It'd be very difficult govern as the chief executive if the country and world sees you as a convicted criminal. Depending on how that plays out, Kaine would most likely take over.
Based on my take of Obama as a person, I'm pretty sure he'd require her stepping down as a condition of a pardon. Otherwise the public would question her legitimacy for four years.
I have no idea if the emails are related enough, as I don't have voting rights in the US I see no reason to care about them.
The Senate is only required to actually convict. It's pretty much a disaster simply to be impeached at all. No conviction is really necessary to permanently damage someone politically.
We've only got one recent example of a President getting impeached, and it worked out pretty well for him.
Or personal pardon!
That would be like Democrats impeaching Bush and getting Cheney instead.
Nothing explicitly prevents it. It doesn't really matter anyhow; Congress has the exclusive power to impeach. Impeachment is the mechanism the constitution provides deal with criminal presidents and the president can't block it.
Make no mistake; the last thing Comey and Clinton+Obama et al. wanted was to fill news cycles with "FBI investigation reopened" 11 days out. It's bad, whatever it is, and this is a CYA move; Comey believes he needs to be able to claim he notified Oversight and made this public prior to the election.
In the current climate, unless a big group of Democrats in the house side with the Republicans on the charges, it can sloughed off as partisan BS.
We'd also probably need some pretty crazy info in those emails to warrant the sharpness of public invective necessary to have a clear political mandate to go through impeachment. It would have to include some of: large scale impact to national interests, beyond-the-pale vile political conspiracy, dick pics of Bill Clinton, or a clear statement of explicit, willfully avoiding public disclosure of the topic of discussion (of particular national interest).
I see the narrative being around "sour grapes losers" and "can't win, can't govern Republicans."
Maybe.... but do the Democrats really want a President that is constantly questioned in terms of her ethics?
I think the Democrats are prepared for that much, at least.