Democratic presidential candidate Hillary Rodham Clinton, whose campaign has been besieged by questions about her use of a private e-mail account to conduct official business while she was secretary of state, acknowledged Sunday that the persistent "drip, drip, drip" has hurt her in the polls but insisted that she has done everything in her power to be transparent.

"This is a contest, and it's fair game for people to raise whatever they choose to raise...you know they're not giving this job away," Clinton said during an interview with NBC News' Chuck Todd on "Meet the Press." "Of course I take responsibility. It was my choice. It was a mistake back when I did it, and I'm trying to do the best I can to answer all of the questions that people have."

For months, Republicans have raised questions about thousands of e-mails sent and received by Clinton from a private account while at the State Department that were then deleted from her private server. Clinton has insisted that she turned over all government-related e-mails, in addition to some personal ones. However, media reports containing new details have undermined some of her claims.

"It's like a drip, drip, drip, and that's why I said that there's only so much that I can control," Clinton said, declining to assure supporters that no further questions would be raised about the accuracy of her statements about the e-mails. "I can't predict to you what the Republicans will come up with, what kind of charges or claims they might make...I can only do the best I can to try to respond."

Clinton and her campaign have maintained that she deleted only personal e-mails from the server and that all government-related e-mails were provided to the State Department. However, new disclosures by federal officials have raised new questions about Clinton's claims.

Officials with the State Department told The Washington Post last week that their request for Clinton to turn over her e-mails was not part of a standard operating procedure, as she has maintained, and that they asked specifically after discovering that she was exclusively using a private account for government work.

And State Department officials said late last week that they were provided with a new e-mail chain that shows Clinton corresponding with Gen. David Petraeus in January 2009 — which contradicts the Clinton campaign's insistence that she did not begin using her "hdr22@clintonemail.com" e-mail address until March 2009.

Clinton said Sunday that she was not directly involved in her lawyers' review of her e-mail server.

"All I can tell you is that when my attorneys conducted this exhaustive process, I didn't participate. I didn't look at them." she said. "I wanted them to be as clear as possible. They didn't need me looking over their shoulder."

When Todd asked about the theory that Clinton may have used a private e-mail account to make it more difficult to access her messages via subpoena or Freedom of Information Act requests, Clinton dismissed the question as "another conspiracy theory."

"It's totally ridiculous. That never crossed my mind," she said, likening the GOP scrutiny of her e-mails to the scandals that plagued her husband, former president Bill Clinton, during the 1990s. "During the '90s, there were a bunch of them. All of them turned out to be not true — that was the outcome. When I ran for the Senate, the voters of New York, they overlooked all of that...and I was elected senator after going through years of this kind of back and forth. It is regrettable, but it is part of the system."