To those who don't want to read the article: the investigation is over a large campaign donation given by a Chinese national (A member of the Chinese government in fact). This would only be illegal if the donor did not have a green card, which the McAuliffe camp says he did
If the Chinese national had a green card at the time of the donation: McAuliffe is in the clear.
No green card: McAuliffe is in trouble.
One would think this would be a fairly straightforward matter to clear up and not take a whole year of investigation.