For now, federal authorities characterize the Justice Department inquiry into Hillary Clinton's private email server as a security situation: a simple matter of finding out whether classified information leaked out during her tenure as secretary of state, and where it went.
Except, former government officials said, that's not going to be so simple.
"I think that the FBI will be moving with all deliberate speed to determine whether there were serious breaches of national security here," said Ron Hosko, who used to lead the FBI's criminal investigative division.
He said agents will direct their questions not just at Clinton, but also her close associates at the State Department and beyond.
"I would want to know how did this occur to begin with, who knew, who approved," Hosko said.
Authorities are asking whether Clinton or her aides mishandled secrets about the Benghazi attacks and other subjects by corresponding about them in emails.
For her part, Clinton said she did not use that email account to send or receive anything marked classified.
"Whether it was a personal account or a government account, I did not send classified material, and I did not receive any material that was marked or designated classified which is the way you know whether something is," she said Tuesday in a question-and-answer session with reporters.
Why is Clinton emphasizing the idea that none of those messages were marked? Because what she knew — her intent — matters a lot under the law. If the Justice Department and FBI inquiry turns into a formal criminal investigation.
Two lawyers familiar with the inquiry told NPR that a formal criminal investigation is under consideration and could happen soon — although they caution that Clinton herself may not be the target.
The Clinton campaign maintains that Clinton did nothing wrong, that the government inquiry would not move beyond a "security-related review" and points a finger at a "culture of classification" within the intelligence community.
"She was at worst a passive recipient of unwitting information that subsequently became deemed as classified," said Brian Fallon, Clinton campaign press secretary, in a conference call Wednesday with reporters, per NPR's Tamara Keith. "When it comes to classified information, the standards are not at all black and white, and in the absence of markings that officially designate something classified, reasonable people each taking their responsibilities extremely seriously, can nonetheless disagree on the character of the information they are dealing with — and both could be completely justified in that perspective.
"And that is why we are so confident that this review will remain a security-related review. We think that furthermore this matter is mostly just shining a spotlight on a culture of classification that exists within certain corners of the government, especially the intelligence community."
Michael Mukasey, who served as attorney general in the George W. Bush administration, recently talked to Newsmax TV about the government's burden of proof.
"They'd have to show that she was responsible for having the information on that server and essentially knew what was on there," Mukasey said.
Whether or not the emails were labeled as secret, some other Republicans say Clinton should have known better.
Former NSA Director Michael Hayden told the MSNBC program Morning Joe: "Put legality aside for just a second, it's stupid and dangerous."
Clinton said she's cooperating with investigators. She has turned over 55,000 pages of emails for review. Inspectors general and members of the intelligence community are sifting through them now. And watchdog groups are in court demanding their public release.
But Clinton's lawyer says she's already deleted thousands more personal email messages. Republicans in Congress are asking about her motivations and soon federal agents may be, too.
"Then we get to the questions about what did Congress subpoena, when did they subpoena it and what was the intent ... if information was deleted or if it was wiped after that time?" Hosko asked.
There's no evidence to suggest those messages were deleted after Clinton got a subpoena this year from the House Select Committee on Benghazi, something that would raise allegations of obstructing justice.
On the campaign trail this week, a reporter asked Clinton if she had wiped clean the server. Her reply? "What like with a cloth or something? Well no I don't know how it works digitally at all."
Clinton later added: "I'm very comfortable that this will eventually get resolved and the American people will have plenty of time to figure it out."
As the campaign intensifies, the FBI and its director, James Comey, will be operating in an environment filled with political sensitivity. But it won't be the first time, Hosko said.
"The FBI won't be ignorant to the political realities," he said, "but they have a job to do, they know that job, they've done it before, they will do it here."