Emails remain a political migraine for Hillary Clinton —  and Trump pounces on them in debate

No issue has dogged Hillary Clinton’s campaign more than her decision to use a private email server while she was secretary of State, and Donald Trump tried to maximize the political pain with sharp sparring Sunday.

Clinton sought to quickly dispatch with the email question by apologizing for using the server but insisting that the nation’s security was not breached by the misstep.

“It was a mistake, and I take responsibility,” Clinton said. “I am very committed to taking classified information seriously. And as I said, there is no evidence that any classified information ended up in the wrong hands.”

Trump would not let that go without rebuttal: “And yet, she didn’t know the letter ‘C’ on a document?” he said about the identifying key for confidential information.

“She’s lying,” he said.

“Do you think it was fine to delete 33,000 emails? I don’t think so,” Trump went on. “You should be ashamed of yourself.”

“It’s just not true,” Clinton shot back.

“You didn’t delete 33,000?”

“Well, we turned over 35,000,” she said.

Moderators tried to get the candidates back on track to debate questions from the audience.

“I’d like to get to the questions people have brought,” Clinton agreed.

“And get off this question,” Trump said.

The email issue has spawned congressional investigations by Republicans, a criminal review by the FBI and a torrent of political attacks.

Clinton initially tried to quell the controversy by telling reporters that she didn’t break any rules by using the server located in the basement of her home in Chappaqua, N.Y.

But that didn’t satisfy Clinton’s critics, especially when she said her team deleted half of her emails — she said they weren’t related to her job — before turning over the rest to the State Department.

As officials reviewed the emails before releasing them to the public, they found information on some that was deemed classified, although Clinton has disputed that the emails were marked classified at the time they were sent. Intelligence officials have said she and her staffers should have known the information was secret.

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When the nearly yearlong investigation was finished, FBI Director James B. Comey said Clinton and her aides should not face criminal charges.

“No reasonable prosecutor would bring such a case,” Comey said. The Department of Justice closed the investigation.

But it was not a clean bill of health. Comey said Clinton had been “extremely careless” in handling classified information. In addition, although Clinton said she didn’t send any emails containing information marked classified, Comey said a handful “bore markings indicating the presence of classified information.”

Agents found that 110 emails containing information that was classified when the messages were sent, according to Comey. Eight email chains contained information that was top secret, the highest level of classification.

The FBI also found some work-related emails that weren’t turned over by Clinton’s team, even though she had said only personal messages were deleted.

Clinton’s statements about the server have evolved over time.

At first she declined to apologize because “what I did was allowed.” But she later expressed regret about using a private account.

“That was a mistake. I’m sorry about that. I take responsibility,” Clinton told ABC.

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Twitter: @chrismegerian; @LisaMascaro

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