Comey crossed the line when he did his press conference and testified on the case in Congress, which was the original sin. He wanted to look impartial, but making that exception specifically for the Clinton case is anything but impartial. If he refused to comment from the beginning, as he should have done, and as happens for pretty much all cases, he would not be on the hook for commenting when new information arises. He decided to make an exception for Clinton investigation, and now he is stuck basically doing something that is the opposite of what FBI should be doing, spreading findings that even his own agency hasn't looked into yet, and thus interfering in the election. Now he is damned whatever he does, but that was his decision to go down this road. He can no longer function as an FBI director. The only way out for him is to accept responsibility and resign.