In recent weeks, she has either dismissed the controversy or joked about it. But on Wednesday she said she had made a mistake.
"My use of personal email was allowed by the State Department. It clearly wasn't the best choice. I should have used two emails -- one personal, one for work -- and I take responsibility for that decision," she said when asked at an Iowa event.
The answer shows much more contrition than she has of late, even acknowledging that she understands why people care about the issue.
"Well, I know people have raised questions about my email use as secretary of state, and I understand why. I get it," she said during a press conference at a local community college.
This is a departure for Clinton, who in past answers has been combative -- and at times joked -- about whether the issue matters at all.
In Nevada earlier this month, for example, Clinton said her email use was normal.
"Everybody is acting like this first time this has ever happened. It happens all the time," she said.
When a reporter pressed her about the issue growing until Election Day, Clinton shot back, "Nobody talks to me about it, other than you guys."
And she generated headlines when, speaking in Iowa earlier this month, she espoused praise for the social message app Snapchat
because, she said, "Those messages disappear all by themselves."
Clinton came to Iowa looking to move past the stories swirling around her campaign. In front of an audience of 200 people at the Des Moines Area Community College, the 2016 candidate pitched her plan for rural America, focusing on more spending for government programs that provide capital and credit to rural business owners, farmers and ranchers.
With former Iowa Gov. Tom Vilsack standing beside her, Clinton called for the creation of a "national infrastructure bank" that would invest in projects looking to "improve the country's rural transportation, water and broadband infrastructure."
"I want America to be in the future business, too, and I believe a strong America depends on strong rural communities," she said.
Making this pitch in Iowa was a no-brainer for Clinton. In addition to the state being the site of the first caucus in the 2016 calendar, more than 35% of Iowans live in rural settings.
Clinton also proposed "strengthening" the Renewable Fuel Standard, a federal rule that requires gasoline to be comprised of up to 10% in renewable fuels. The issue is critically important to Iowa, the top corn-producing state in the nation.
The former secretary of state said she would "expand the overall contribution that renewable fuels make to our national fuel supply" as president.
While her statement was heralded by Iowans and ethanol advocates, Clinton has not always been for strengthening ethanol. In a 2002 debate over an energy bill, Clinton derided a then-pending requirement that two billion gallons of corn ethanol be blended into domestic gasoline per year.
"We are providing a single industry with a guaranteed market for its products -- subsidies on top of subsidies on top of subsidies, and, on top of that, protection from liability," Clinton said in 2002
. "What a sweetheart deal."
But in a May op-ed
, Clinton said it was time to get the fuel standard "back on track."
Vilsack, who formally endorsed Clinton on Tuesday in an op-ed, offered an impassioned defense of Clinton on Wednesday, speaking to both her personal character and her conviction for the job she seeks.
"I know of no one in America today who is tougher and more tested than Hillary Clinton," he said, calling his decision to endorse her "an extremely personal" one. "She is the best candidate from my party to win this election."