Sen. Joni Ernst, R-Iowa, said at a recent town hall that lawmakers should discuss fixing Social Security "behind closed doors," prompting a wave of criticism from liberal and advocacy groups.

Ernst, who is running for reelection in 2020, made the remarks Saturday in Estherville, Iowa, according to a video posted by the Democratic super PAC American Bridge. The comments began to receive broader attention after they were reported Wednesday by the liberal news website Iowa Starting Line.

Ernst told the audience that "there is a point in time when we as Congress will have to address the situation. And I think it's better done sooner rather than later, to make sure that we've shored up that system."

"So it's, you know, a broader discussion for another day," she added. "But I do think, as various parties and members of Congress, we need to sit down behind closed doors so we're not being scrutinized by this group or the other, and just have an open and honest conversation about what are some of the ideas that we have for maintaining Social Security in the future."

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Senior citizens make up a significant portion of the Iowa electorate. U.S. Census figures show that 14.9% of Iowa's population was 65 or older in 2010. Only Florida (17.3%), Maine (15.9%), Pennsylvania (15.4%) and West Virginia (16%) had higher percentages.

So far, four Democrats have announced bids against Ernst in 2020. One of them, real estate executive Theresa Greenfield, raised the issue of Social Security at a campaign event Saturday, according to the Dubuque Telegraph Herald, as well as in recent tweets.

"The only people squealing from Joni Ernst's toxic record are Iowans who rely on Social Security," Greenfield tweeted Wednesday, in a reference to a 2014 campaign ad by Ernst about castrating hogs. "We work hard for these earned benefits and deserve better than a senator who plays games with retirement security."

American Bridge and other groups also seized on Ernst's remarks.

"@SenJoniErnst's plan to privatize Social Security is so toxic, she wants to keep it a secret to avoid 'media scrutiny,' " the super PAC said in a tweet.

Ernst did not mention privatizing Social Security in her town hall remarks. She has previously mentioned private accounts as one "option" among many that lawmakers should examine, "because we really don't know which way is the best way to go yet," according to the Des Moines Register.

The advocacy organization Social Security Works accused Ernst of seeking to "cut our earned benefits in secret."

Ernst's Senate office did not immediately respond to a request for comment on the criticism of her remarks.

The statements by Democrats, however, appeared to reinforce the very point that Ernst was trying to make at her town hall, where she said that many members of Congress are afraid to raise the issue of Social Security because of political attacks.

"I will tell you that there are very few members of Congress that even want to broach the subject, because it's become so controversial," she said Saturday. "And anything you say — 'we need to address Social Security' — the media is hammering you. The opposing party will hammer you: 'There goes Granny over a cliff.' There is a real issue out there."