AMES, Iowa — Facing a narrowing primary contest, Hillary Clinton ripped into rival Bernie Sanders on Tuesday, saying the Vermont senator was offering unrealistic policies and overstating his anti-establishment credentials.

For days, Clinton has cast Sanders as a less forceful advocate for gun control, honing in on a 2005 vote he cast that gave immunity to gun manufacturers. On Tuesday, she broadened her critique, arguing that if Sanders wouldn’t combat the National Rifle Association, he can’t be trusted to take on other special interests.

“If you’re going to go around saying you stand up to special interests then stand up to that most powerful special interest — stand up to the gun lobby,” she said, as she accepted the backing of a major gun control advocacy group.

Clinton added: “Don’t talk to me about standing up to corporate interests and big powers. I’ve got the scars to show for it.”

The fresh critique marks an effort by Clinton to undermine the central argument of Sanders’ campaign— that the Vermont senator is an outsider offering liberals a “political revolution.” At one point, she alluded to his mantra, telling supporters, “If that’s the kind of ‘revolution’ he’s talking about, I’m worried, folks.”

With a touch of sarcasm, Clinton said President Barack Obama’s work to pass an overhaul to the nation’s health care system was a major accomplishment and derided Sanders’ plans for a single-payer Medicare-for-all system.

“I wish that we could elect a Democrat who could wave a magic wand and say, ‘we shall do this and we shall do that.’ That ain’t the real world we’re living in!” Clinton said.

Clinton also touted her foreign policy credentials, drawing another, more implicit, contrast with Sanders, who has made tackling economic inequality the focus of his campaign. “I’m prepared to do all parts to the job,” she said, after offering voters a detailed account of her time in the Situation Room during the killing of Osama bin Laden.

Though Clinton has the backing of Democratic leaders and top donors, polls show a tighter race in Iowa while Sanders has built a slight lead in New Hampshire, which borders his home state of Vermont. Losses in both early voting states could raise worries among Democrats about her strength against Sanders, who was relatively unknown when he started the campaign but has attracted big crowds to his rallies.

A poll released on Wednesday by Quinnipiac University showed Sanders winning 49 percent of likely Democratic caucus-goers in Iowa, compared to 44 percent for Clinton. The same survey showed Clinton leading in a 51-40 percent match-up just a month ago.

Clinton has long resisted directly targeting Sanders, fearing that such attacks would alienate his passionate supporters. Should she win the nomination, Clinton will need that kind of liberal enthusiasm to boost her to victory in a general election.

Daughter Chelsea Clinton also got in the act, telling a New Hampshire audience that Sanders would open the door for Republican governors to undermine the health care law.

“I never thought we’d be arguing about the Affordable Care Act in the Democratic primary,” she said. “Sen. Sanders wants to dismantle Obamacare, dismantle the (Children’s Health Insurance Program), dismantle Medicare, dismantle private insurance.”

Both candidates received dueling endorsements on the eve of Obama’s State of the Union address. Clinton picked up the backing of the Brady Campaign to Prevent Gun Violence — an endorsement that came just a day after she won support from leading gun control advocate Gabby Giffords, the former Arizona congresswoman and her husband Mark Kelly.

Dan Gross, president of the Brady Campaign, noted that the two candidates diverged on the landmark Brady handgun bill, which imposed a five-day waiting period for gun purchases. “Bernie Sanders actually voted against it. But there’s only one candidate who fought for it and that candidate is Hillary,” he said.

Sanders has expressed his support for Obama’s use of executive actions to curb gun violence and has said he would revisit his position on the liability issue. But in a Democratic forum on Monday night, he doubled down on his defense of his vote on the controversial bill.

“It’s not a mistake. Like many pieces of legislation, it is complicated,” he said. “But on the issue of guns, let me be very clear I support the president.”

Clinton was also endorsed by the United Food and Commercial Workers Union, a union of 1.3 million members.

Sanders racked up his own endorsement on Tuesday, receiving the backing of MoveOn.org, a grassroots organization that has been at the forefront of liberal causes.

He was supported by 78.6 percent of its membership in an online vote of more than 340,000 members, according to the group. Hillary Clinton received 14.6 percent and Martin O’Malley received 0.9 percent with the remaining members urging no endorsement. The group said it plans to mobilize thousands of its members in Iowa and New Hampshire on Sanders’ behalf.