The report on Hillary Clinton’s email by the State Department’s inspector general this week was devastating — not because of how she handled email but because of how she handled investigators.

The report’s revelations weren’t particularly revelatory: Clinton violated department policies and went further than predecessors in her use of private email, but she wasn’t the first to take this path. Beyond that, as my colleagues Rosalind Helderman and Tom Hamburger reported, officials say the FBI has “found little evidence that Clinton maliciously flouted classification rules.”

But what’s damning in the new report is her obsessive and counterproductive secrecy:

The Office of the Inspector General said it “interviewed Secretary Kerry and former Secretaries Albright, Powell, and Rice. Through her counsel, Secretary Clinton declined OIG’s request for an interview.”

“In addition to Secretary Clinton, eight former Department employees [most of them Clinton aides] declined OIG requests for interviews.”

The Inspector General's office said on May 25 that former Secretary of State Hillary Clinton's use of a personal email account was “not an appropriate method” for preserving those emails. (Peter Stevenson,Sarah Parnass/The Washington Post)

“Two additional individuals did not respond to OIG interview requests.”

“OIG sent 26 questionnaires to Secretary Clinton’s staff and received 5 responses.”

The stonewalling creates a firm impression, well captured by CNN’s Wolf Blitzer this week when he interviewed Clinton’s spokesman, Brian Fallon: “If she didn’t do anything wrong and she had nothing to hide, why didn’t she cooperate with the inspector general?”

There is no good answer to this. And that’s why the IG report was just another of Clinton’s self-inflicted wounds, stretching back a quarter century, caused by her tendency toward secrecy and debilitating caution.

Donald Trump has decided to dub her “Crooked Hillary.” This isn’t quite true: Though investigations into her activities have occupied much of the past 25 years, her accusers, on Whitewater to Benghazi, never really get the goods. But what Clinton has been is nearly as problematic as being crooked: Hunkered Hillary. At the first sign of conflict or accusation, Clinton circles the wagons, shuts her mouth and instructs those around her to do the same. This generates a whole lot of smoke, even if there’s no fire. Her secrecy elevates the accusations — whatever the accusations are.

Fifteen months ago, when the email scandal broke, I viewed her use of a private server as an extension of the “same flaws that have caused Clinton trouble in the past — terminal caution and its cousin, obsessive secrecy. In trying so hard to avoid mistakes — in this case, trying to make sure an embarrassing e-mail or two didn’t become public — Clinton made a whopper of an error.”

She resisted releasing records on the Whitewater land deal (causing the scandal to drag on, leading to the independent-counsel investigation that exposed the Monica Lewinsky-Bill Clinton scandal) and about her 1993 health-care task force (giving her opponents ammunition to defeat the plan). She again hunkered down.

1 of 9 Full Screen Autoplay Close Skip Ad × Takeaways from Hillary Clinton’s e-mails View Photos Clinton has come under fire for using a private e-mail address during her time as secretary of state. The emails are being screened and released in batches. Here are some things we’ve learned from them. Caption Clinton has come under fire for using a private email address during her time as secretary of state. The emails are being screened and released in batches. Here are some things we’ve learned from them. Top-secret information in e-mails Democratic presidential candidate Hillary Clinton has previously stated that classified information never traveled across her private server. However, the State Department has acknowledged that "top secret" information was in seven email chains sent or received by her. Richard Drew/AP Buy Photo Wait 1 second to continue.

Clinton’s response is emblematic of her caution. While Trump and Bernie Sanders drive the narrative of the 2016 campaign with their freewheeling styles, Clinton is missing: She puts herself into the debate less often than the others, and, when she does, she says little to merit headlines. Her hiring of a full slate of advisers to President Obama — himself a cautious leader — reinforces the risk aversion. But caution won’t win this year, and it’s unclear whether Hunkered Hillary will, or even can, liberate herself from the bunker.

The inspector general’s bottom line wasn’t good: “She did not comply with the Department’s policies.” But the description of Clinton’s secrecy was worse. When one State Department staffer raised concern about Clinton’s private email, this person was told “that the secretary’s personal system had been reviewed and approved by department legal staff and that the matter was not to be discussed any further.” Investigators found no evidence of such a review.

What they found was stonewalling by Clinton and her aides — and this, not mishandled email, is what tripped up Fallon as he tried to defend the candidate to Blitzer.

“It looks as if she’s got something to hide when she doesn’t even want to answer questions from the inspector general of the State Department,” the veteran anchor argued.

Fallon, a skilled flack, tried to argue that Clinton and her aides prioritized the similar Justice Department investigation and were cooperating with that one. Then he insinuated that “there were hints of an anti-Clinton bias” in the IG’s office.

The vast right-wing conspiracy had infiltrated the State Department! Asked Blitzer: “Are you accusing the inspector general of the State Department” — a Democratic appointee — “of having an anti-Clinton bias?”

The spokesman retreated, noting that the report documented “that the use of personal email was widespread and done by her predecessors, including Secretary Powell.”

And that might have been the take-away — if Hunkered Hillary hadn’t let her instinctive caution again get the best of her.

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