After repeatedly declining to apologize, US presidential candidate Hillary Clinton has finally expressed regret for using a private email server during her tenure as secretary of state.

The Democratic front-runner acknowledged for the first time on Tuesday that her use of the private server while she was the head of the US State Department between 2009 and 2013 was a “mistake.”

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

“I do think I could have and should have done a better job answering questions earlier. I really didn’t perhaps appreciate the need to do that,” she added.

For months, Clinton tried to minimize or dismiss the controversy, but has concluded she needs to adjust course since the issue has been weighing heavily on her popularity amid a big slide in the polls.

Her apology on ABC was more striking as it came just a day after an interview with The Associated Press in which she maintained that she did not need to apologize for not using a government server while she was the top diplomat, saying, “What I did was allowed.”

When asked last week by NBC News if she was sorry, she declined the opportunity to apologize. “Well, I certainly wish that I had made a different choice,” she said then, adding that she was “sorry that this has been confusing to people.”

The former top diplomat denies receiving or sending any emails containing classified information at the time. But many of the thousands of emails she later turned over to the State Department are said to contain top secret information.

The FBI is examining the server to determine whether the arrangement compromised government secrets.

A poll released Tuesday by Monmouth University found that support among Democratic and Democratic-leaning voters across the country for Clinton has declined 10 points in the last month, to 42 percent.

The poll showed many Democratic voters in New Hampshire cited Clinton’s personal email use as a problem for them.