There is a reason that Trump has been screaming that the whole thing is rigged The reason is simple when you don't give a damn about the institution , in this case the electoral system, win or lose you can claim victory.

But more importantly it influences the way justice is served on you.

DoJ IG report lesson: GOP bullying of law enforcement works

Trumps cries of unfair treatment did change the way he was treated.

Which brings in the next test for DOJ. Will Robert Mueller subpoena Donald Trump? it seems pretty clear he can...it has been done before. And in My opinion it has to be done here. If he doesn't it will prove that he is above the law and that Mueller has no power.

In short if he doesn't subpoena Trump the investigation is over...Trump wins.