In his handling of the Clinton email case, FBI Director James Comey has demonstrated both poor judgment and a startling inability to handle the political heat that comes with his job. Under pressure, he has made a series of significant blunders that have placed the FBI in a position in which it must never ever be, which is right in the middle of a presidential campaign coming into its final days.

The fact that Comey made these errors in a badly botched effort to protect his own political reputation and that of his agency just compounds the gravity of his mistake. His concern for those matters is understandable; his decision to give them a higher priority than the fair running of a presidential election is not.

He ought to resign, effective before the next president takes office.

Comey's most recent and most serious mistake was to announce Friday afternoon, just 11 days before the election, that possibly pertinent emails of unknown significance to the Clinton case had been found stored in an electronic device discovered in an unrelated case. Leaked information shortly thereafter established that the emails had been found during an investigation of the Typhoid Mary of American politics, one Anthony Weiner of New York.

Reportedly, none of the emails had been sent by Hillary Clinton; reportedly, there is no suspicion that the emails had been withheld or hidden from the investigation. But in publicly announcing their existence, Comey violated longstanding Justice Department policy, traditions and procedures and in the process set off an entirely predictable political firestorm.

Within minutes of Comey's statement, U.S. Rep. Jason Chaffetz, chairman of the House Oversight Committee, gleefully announced that the FBI had reopened its Clinton investigation. (It has not.) On the campaign trail, Donald Trump proclaimed the case to be "bigger than Watergate," a description that the Washington Post -- which ought to know about Watergate -- describes as absurd and worthy of four Pinocchios. Newt Gingrich, deploying his finely honed instinct for understatement, claimed it to be "at least 50 times bigger than Watergate," which if you do the math puts him at 200 Pinocchios.

In his terse public statement Friday, Comey admitted that he and his agents have no idea about the possible significance of the emails, which may very well prove to be just duplicates of emails already discovered and processed, as has been the case with earlier, much-ballyhooed discovery of "new emails." In an internal memo to his employees, he also acknowledged a high probability that hise announcement would be misinterpreted.

So if the department itself has no idea of the potential significance of these emails, if any, how on earth are voters supposed to make sense of it all? If Comey knew that his announcement was likely to be misinterpreted, why make that announcement in the first place?

As you may recall, we in Georgia have witnessed how this process is supposed to work firsthand, and why adhering to that process is important.

Back in 2011, the FBI opened an investigation into allegations against Gov. Nathan Deal, possibly looking into misspent campaign funds, misuse of federal taxpayer money as a member of Congress to help his state campaign, his actions in strong-arming state officials to protect a state-granted monopoly for his auto-salvage business, and the removal of state ethics commission employees who had dared to investigate him.

Despite its political implications, we don't know the exact parameters of that case because it was never explained to us.  Throughout the investigation, which stretched into Deal's re-election year of 2014, FBI officials followed policy by refusing to comment or to acknowledge the probe even existed. They released no daily updates on the various twists and turns of their investigation, and their activity became known only through actions that they were forced to take publicly, such as when it issued subpoenas and summoned state ethics-commission employees to testify to a secret grand jury.

Even when the investigation ended without charges, it did so quietly. The FBI made no announcement about closing a probe that it had never admitted beginning in the first place, and it never commented on the propriety of Deal's behavior in any way. Either it had enough evidence to prosecute Deal or it did not, and it concluded that it did not.

That's how such things are done, by longstanding practice and FBI policy, and the reasoning behind it is fundamentally sound. An investigation is not an indictment, just as an indictment is not a conviction, and the mere existence of an investigation tells you nothing. There is no legitimate reason why the Clinton investigation should have been handled any differently than the Deal investigation or the tens of thousands of other investigations over the years that the FBI has quietly opened and quietly closed. Yet it clearly was.

We don't know the political impact of this late-breaking development, and may not until Election Day. My own sense is that its impact will be small, but that's just a guess. However, it is certainly plausible to imagine a scenario in which it gives Trump a narrow victory, after which we all discover that these new emails were totally innocuous after all, with no real consequence other than to change the course of an election and with it the course of U.S. history.

That is precisely the nightmare scenario that FBI policy and precedent are designed to avoid. And that is precisely the scenario that Comey has made plausible.