Democratic presidential candidate Hillary Clinton speaks during a campaign rally in North Liberty, Iowa, on Jan. 24 ahead of the caucuses in Iowa. (Jim Watson/AFP/Getty Images)

Hillary Clinton agreed she made an error by using a private email server as secretary of state.

Until, it seemed, she didn’t.

In September, under significant pressure even from political allies to apologize for her private email use, Clinton called the set-up “a mistake.”

“I’m sorry about that,” she said.

But in a town hall broadcast on CNN on Monday in which the Democratic candidates made their final televised pitches before next week’s Iowa caucuses, Clinton seemed to walk back that apology.

“I’m not willing to say it was an error in judgment because what — nothing that I did was wrong,” she said. “It was not in any way prohibited.”

It was a brief moment of uncertainty during an appearance where Clinton otherwise appeared feisty and energized — and a troublesome reminder for Clinton of the ways in which the email controversy continues to fester for her campaign.

David Axelrod, a former adviser to President Obama who had urged Clinton to apologize over the emails, told CNN on Tuesday that Clinton’s answer at the town hall “kind of contradicts” her earlier apology.

While generally giving her high marks for her performance, Axelrod said, “She’s still having trouble with that question.”

Clinton press secretary Brian Fallon said Clinton is not reopening the issue.

“As Hillary Clinton has said before, it was a mistake not to use two accounts,” he said. “She regrets that decision, and has taken responsibility for it.”

The issue has been less politically problematic for her in recent weeks — even as the campaign for the Democratic nomination has become more competitive — because her chief rival, Sen. Bernie Sanders (Vt.), has declined to wield it against Clinton. (Sanders closed the door to the issue during an October debate, declaring that Americans were “sick and tired” of hearing about Clinton’s “damn emails.”)

But Clinton’s email use has continued to animate her potential Republican opponents, who have made clear it will be a central plank of their argument against her should she win the Democratic nomination.

In Washington, the issue has hardly died, either.

The FBI continues to investigate the security of Clinton’s email arrangement, particularly whether it could have led to the inappropriate handling of classified information. The State Department’s inspector general is also looking into the use of private emails at the State Department. A report from the agency watchdog is expected to land at some point during the campaign.

The issue of whether Clinton’s system invited sloppy handling of state secrets also has not disappeared.

The inspector general of the intelligence community told congressional oversight committees in a letter released last week that some information found in Clinton’s emails was classified “top secret” and related to “special access programs,” meaning it concerned some of the nation’s most closely guarded secrets.

Clinton’s campaign has rejected the assessment, with campaign spokesman Brian Fallon, in an appearance on CNN, accusing Inspector General Charles McCullough of working with Senate Republicans to engage in a “very coordinated leak” to damage Clinton politically.

She has continued to maintain that none of the emails she sent or received were marked classified while she was secretary of state. And she has chalked up some of the more recent assessments that the correspondence included sensitive material to a fight between governmental agencies about how to classify the material.

That explanation been supported so far by the State Department, where officials have declined to label any of Clinton’s emails “top secret,” the highest ranking of classified material.

The State Department has been releasing Clinton’s correspondence in batches each month since the summer, redacting some information because the agency’s reviewers have deemed it classified. So far, the State Department’s reviewers have said more than 1,300 emails included classified material. However, they have indicated that all of those emails were “confidential” or “secret” — not as sensitive as “top secret.”

That could change as the State Department prepares to release the last of Clinton’s emails — those whose review took the most time because they required analysis by multiple government agencies, including some in the intelligence community, before they could be made public.

The “review process is still ongoing, and once that process is complete, if it is determined that information should be classified as ‘top secret’, then we’ll do so,” State Department spokesman John Kirby told reporters last week.

At Monday’s town hall, Clinton stressed her desire to see all of her emails made public.

“I think it’s great. Let people sort them through,” she said. “But it’s something that took time to get done.”

In fact, the State Department has indicated that sorting through Clinton’s emails will take longer than expected. A federal judge had ordered the agency to release all of Clinton’s emails by the end of this month. Last week, lawyers for the agency asked the judge to give the department until the end of February to complete the process, meaning Clinton’s emails could still be emerging even after the Iowa caucuses and New Hampshire primary.

Anne Gearan in Des Moines contributed to this report.