A day after again declining to apologize for her use of a private email system while she was secretary of state, Hillary Rodham Clinton told an interviewer on Tuesday that the arrangement was a mistake and that she is “sorry” for it.

“That was a mistake. I’m sorry about that. I take responsibility,” Clinton said in an interview with ABC News.

The statement was the furthest Clinton has gone in showing remorse for the arrangement, which mingled her work and personal communications and kept them outside the regular State Department email system. The FBI is investigating whether the system, maintained on a privately owned computer server at Clinton’s New York home, jeopardized classified information.

In interviews on Friday with NBC and on Monday with the Associated Press, Clinton had declined to apologize, even as she said the arrangement was a poor choice that she regrets. She told NBC interviewer Andrea Mitchell that she is sorry the issue is confusing for people, but insisted that she had done nothing wrong.

She would not apologize, she told the AP, because “what I did was allowed.”

Republican critics had begun to use the question of an apology against her, undermining the campaign’s plan to address the complex email issue more directly and with greater humility. Questions about the private system have contributed to Clinton’s slide in the polls, with more people saying they do not trust her.

A Washington Post/ABC News poll this month found that 53 percent of Americans now see Clinton unfavorably. That rating rose by 8 percentage points since earlier in the summer, tipping the balance to a majority of Americans now seeing her in an unfavorable light.

Clinton turned over copies of roughly 30,000 emails at the State Department’s request late last year, nearly two years after she left office. At the same time she directed that a slightly larger number of emails stored on the server be destroyed because she deemed them personal and not part of her government business. Initially she refused to turn over the server, but did so in August.

Clinton told ABC that she did not send or receive classified material on the account and said she is “trying to be as transparent as I possibly can.”

Portions of the ABC interview were set to air on the Tuesday evening newscast, and later on Nightline.

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