WASHINGTON — Democratic presidential candidate Hillary Rodham Clinton, whose campaign has been besieged by questions about her use of a private email 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.