The private email server Hillary Clinton used while secretary of State reemerged as a liability for her presidential run, as the State Department acknowledged Friday that 22 messages stored on the server contain top-secret information.
Clinton has long denied any of the messages that went through the unprotected server in her home contained highly sensitive material. The State Department said none of the messages were marked top secret at the time they were sent -- although it is looking into whether they should have been.
The administration refused to discuss the contents of the messages, which it acknowledged hours before the latest batch of about 1,000 pages of Clinton email is to be disclosed publicly. The messages marked top secret are being excluded from the disclosure.
"I'm not going to speak to the content of these documents," said State Department spokesman John Kirby at a briefing with reporters. "I understand there's great curiosity. I'm just going to put that right out at the top. I am not going to speak to the content of this email traffic."
He said the documents have been marked as highly sensitive "at the request of the intelligence community because they contain a category of top-secret information."
The Clinton campaign issued a statement Friday denying the documents contain any sensitive government secrets.
"We firmly oppose the complete blocking of the release of these emails," spokesman Brian Fallon said.
"After a process that has been dominated by bureaucratic infighting that has too often played out in public view, the loudest and leakiest participants in this interagency dispute have now prevailed in blocking any release of these emails. This flies in the face of the fact that these emails were unmarked at the time they were sent, and have been called 'innocuous' by certain intelligence officials."
The campaign also said the emails were never previously classified by the State Department because there was nothing sensitive in them. One of the emails, the statement said, focuses on the contents of a published news article.
"This appears to be over-classification run amok," the campaign said.
Intelligence agencies typically take the position that information deemed classified remains so even if it has been publicly revealed and widely discussed. As a result, an email discussing a news story about a classified program could be considered classified. How many of Clinton's emails fall into that sort of category is not known.
Sen. Dianne Feinstein (D-Calif.), the top Democrat on the Senate Intelligence Committee, said the emails in question were part of seven separate "back-and-forth email chains," and that none originated with Clinton. None of the emails she received had the mandatory markings required when classified information is transmitted, Feinstein added.
"It has never made sense to me that Secretary Clinton can be held responsible for email exchanges that originated with someone else," said Feinstein, who has endorsed Clinton. "The only reason to hold Secretary Clinton responsible for emails that didn't originate with her is for political points, and that's what we've seen over the past several months."
The latest iteration of Clinton's email troubles comes as an unwelcome distraction to her campaign, just three days before the first votes are cast in the race for the Democratic nomination. Polls show Clinton and Sen. Bernie Sanders (I-Vt.) are in close to a dead heat in Iowa, which will hold its caucuses Monday.
The emails are the focus of an FBI probe that began six months ago, and could go on for months longer. Even if Clinton is not ultimately found by law enforcement to have done anything wrong, the prospect of an FBI investigation dragging into the general election campaign is unsettling to Democrats.
Despite the campaign's best efforts, Clinton has been unable to put to rest questions about her use of the private server. At a nationally broadcast town hall in Iowa earlier this week, a young voter in the audience asked Clinton to explain why so many voters of his generation don't trust her. She attributed that problem to all the attacks she has endured from political opponents during her long career. But she found herself once again trying to explain why she did nothing inappropriate.
"I'm not willing to say it was an error in judgment because nothing I did was wrong," she said.
Although Clinton's Democratic rivals have avoided attacking her on the email issue, Republicans have pounded her on the topic, and the latest news will undoubtedly figure heavily in their criticisms.
For more on the Clinton campaign, follow @EvanHalper on Twitter.
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