In 2012, Obama was ahead of Romney by double-digits all the way up until the last week when the media outlets felt compelled to retain their credibility by tightening up the polls, restoring them them to actuality. Of course, the larger suspicion this time around is that the inflated poll numbers were designed to make a Trump loss in states like Texas less surprising as she and Soros rig the electronic votes to make them match CNN and friends' projections.
But even if a portion of Hillary supporters would turn away from her over this revelation, it's highly unlikely that the drop would be over a full 12 points--which is what we've been seeing. The two camps are far too galvanized to be disillusioned by anything less than, say, a snuff tape.
As far as Comey is concerned, the alleged FBI agent that posted revealing data on 4chan had already prophesied that he would be pushed up against the wall by his own agency if he didn't act on the intelligence and evidence that they had compiled against Hilldawg. Former FBI agents with ears in on what's going on at the Bureau are telling tales of agents protesting, en masse, Comey's obviously corrupt decision to let her off the hook--whether the evidence incriminated Obama or not. As you say, devil and a deep blue sea.
People shouldn't get it in their heads that this man is principled or has integrity simply because he came forward with this information. He's as pozzed as he ever was--especially with his history of being an executive operator at the Clinton Foundation.
