[Update] It's getting real for Hillary.

For months, the U.S. State Department has stood behind its former boss Hillary Clinton as she has repeatedly said she did not send or receive classified information on her unsecured, private email account, a practice the government forbids.

While the department is now stamping a few dozen of the publicly released emails as "Classified," it stresses this is not evidence of rule-breaking. Those stamps are new, it says, and do not mean the information was classified when Clinton, the Democratic frontrunner in the 2016 presidential election, first sent or received it.

But the details included in those "Classified" stamps — which include a string of dates, letters and numbers describing the nature of the classification — appear to undermine this account, a Reuters examination of the emails and the relevant regulations has found.

The new stamps indicate that some of Clinton's emails from her time as the nation's most senior diplomat are filled with a type of information the U.S. government and the department's own regulations automatically deems classified from the get-go — regardless of whether it is already marked that way or not.

In the small fraction of emails made public so far, Reuters has found at least 30 email threads from 2009, representing scores of individual emails, that include what the State Department's own "Classified" stamps now identify as so-called 'foreign government information.' The U.S. government defines this as any information, written or spoken, provided in confidence to U.S. officials by their foreign counterparts.

[/update]

I'll keep this short.

She broke policy

A federal judge on Thursday said that Hillary Rodham Clinton did not comply with government policies in her exclusive use of a personal email account while she was secretary of state, challenging her longstanding position that she abided by the rules.
At a hearing for a Freedom of Information Act lawsuit against the State Department, the judge, Emmet G. Sullivan of Federal District Court for the District of Columbia, said that “we wouldn’t be here today if the employee had followed government policy.”
Judge Sullivan also opened the door for the F.B.I., which is investigating whether there was classified information on Mrs. Clinton’s account, to expand its inquiry to pursue emails that she may have deleted.

Law Enforcement is investigating

U.S. law enforcement officials are investigating how classified material found its way into messages that members of Hillary Clinton’s State Department staff sent to her private e-mail address, according to a U.S. official with knowledge of the inquiry...
This transfer of classified information onto a server not approved to handle sensitive material is a focus of the investigation and could form the basis for a criminal probe to determine just how much classified material was sent - and who prepared and sent it....
“There’s a responsibility to safeguard classified information,” Michael Hayden, former director of the National Security Agency and CIA, said in a phone interview. Failing to protect such data “could get to a level of negligence that criminal penalties would kick in.”
The probe comes after the inspector general for U.S. intelligence agencies determined that four e-mails on Clinton’s server contained classified information at the time they were sent.

Personally I think the email issues aren't all that important, but her campaign was floundering even before this. This is becoming a real scandal, not a fake one. Even if nothing illegal is turned up, this could easily hang over Hillary's campaign for many months.
And if this turns into criminal charges, even if Hillary is ultimately found innocent, then her campaign would probably be over.
But Hillary is ahead, so how can she be floundering? This is how.

Scroll all the way down to question #46, which asks, "Would you say that Hillary Clinton is honest and trustworthy or not?"

Thirty-two percent of respondents in Florida and Pennsylvania said she was; 34 percent of Ohioans said so. Just in case that's too much math for you: Only one in three voters in the three largest swing states in the country think that the overwhelming favorite for the Democratic nomination is honest and trustworthy.

But wait, you say! Context matters. I bet those same voters trust the Republican frontrunners even less!

Except, again, no.

The only Republican candidate with honest/trustworthy numbers like Clinton is Donald Trump. And, Trump's numbers are still not as bad as Clinton's. His lowest score on the honest/trustworthy measure is in Ohio where just 37 percent of voters say those words describe him.

When The Donald is considered more trustworthy than you, your campaign has a serious problem.

[Update] Hillary's legal defense has holes

Hillary Clinton’s campaign this week stepped up its defense of the Democratic front-runner’s use of a private email server while serving as secretary of state, arguing on Wednesday that Clinton, in the worst-case scenario, was simply a “passive recipient of unwitting information that subsequently became deemed as classified.”

But those with deep expertise in the classification system say it’s not so simple.

While emphasizing that Clinton’s defense cannot be judged until the content of the messages are fully analyzed, fellow diplomats and other specialists said on Thursday that if any emails were blatantly of a sensitive nature, she could have been expected to flag it.

“She might have had some responsibility to blow the whistle,” said former Ambassador Thomas Pickering, who served under the former secretary of state and oversaw a department review of the deadly attack in 2012 on the U.S. consulate in Benghazi, Libya, a subject of some of the most scrutinized of Clinton’s emails.

“The recipient may have an induced kind of responsibility,” Pickering added, “if they see something that appears to be a serious breach of security.”

It is a view shared by J. William Leonard, who between 2002 and 2008 was director of the Information Security Oversight Office, which oversees the government classification system.

He pointed out that all government officials given a security clearance are required to sign a nondisclosure agreement, which states they are responsible if secrets leak – whether the information was “marked or not.”

What's more, Hillary had a history of email security breaches.

Despite a hack two years ago that publicly exposed Hillary Clinton’s emails, the State Department took no action to shore up the security of the former secretary of state’s private computer server.