This post has been updated.

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

“As I look back at it now, even though it was allowed, I should have used two accounts. 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 e-mail 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 Friday with NBC and 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 e-mail 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 e-mails 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 e-mails 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.”

Late Tuesday, the campaign sent a message to supporters in Clinton's name reiterating the apology. Donors and activists have been complaining to the campaign headquarters for weeks that the e-mail issue was being mishandled, and it largely is their concern and disappointment Clinton is trying to head off.

"I wanted you to hear this directly from me," this e-mailed statement to supporters said. "Yes, I should have used two email addresses, one for personal matters and one for my work at the State Department. Not doing so was a mistake. I'm sorry about it, and I take full responsibility."

Clinton went on to stress, as she regularly does, that her personal account was "aboveboard," and that "nothing I ever sent or received was marked classified at the time. "

Despite the campaign’s effort to more directly confront its problems stemming from the e-mail saga, Clinton’s own reckoning with it still seemed grudging.

In March, she insisted that she had done everything by the State Department book and had nothing for which to answer; last month she said that she “gets it” that voters have questions. That was a significant shift — as was the decision to stop insisting the controversy was a manufactured Republican hit job.

But until now, Clinton had always said that although she would make a different choice today, there was nothing inherently wrong with setting up the system as she did.

Clinton’s reversal on making an apology echoed the protracted 2008 campaign discussion of whether she would say she was wrong or sorry about her Senate vote in support of the Iraq war.

In both cases, Clinton adopted a narrow and somewhat lawyerly stance at first, then came to a more direct show of remorse.