Sen. Elizabeth Warren attempted Thursday to move beyond a rocky stretch in her campaign by refocusing on the economic message that helped her rise in the first place, taking the opportunity to aim a series of attacks at her more centrist rivals.

In the tightly crafted speech reiterating the rationale for her candidacy, Warren (D-Mass.) criticized former vice president Joe Biden and South Bend, Ind., Mayor Pete Buttigieg, calling them “naive,” mocking their “vague calls for unity” and suggesting Buttigieg is “beholden” to wealthy donors.

“The rich and powerful have written the rules for our economy so that they suck up all the gains for themselves,” Warren told students at St. Anselm College in New Hampshire. “It’s corruption, plain and simple, and it’s holding back growth and opportunity.”

The message came as Warren tried to regain the momentum she had built over the summer in town hall meetings where she promised a new era of government aimed at providing more power to workers, unions and small businesses.

“Other candidates do not grapple with these fundamental issues of economics and power,” she said Thursday.

Most polls show Warren among the top candidates in the Democratic field, a strong position just weeks before the first voters weigh in during the Iowa caucuses on Feb. 3. But the surveys also reveal that her numbers dropped in the fall as she spent valuable time trying to explain her position on health care.

On Thursday, Warren pledged to tackle three sweeping problems with the economy: the incentive for companies to focus on short-term profits, a lack of competition in some markets, and the twin challenges of stagnant income and rising costs.

But she sought to balance that broad message with a pragmatic tone that has not typically been part of her image — or her stump speech. “Will I have a magic wand to enact my full agenda? Of course not. No president does. I know I will have to compromise,” she said. “But that’s not where we start.”

Warren also appeared to allude to a harsh back-and-forth with Buttigieg, in which the two recently took aim at each other’s time in the private sector, including Warren’s work for corporations when she was a law professor. “Nobody is perfect, and nobody is pure,” Warren said.

Her campaign staff emphasized the contrasts she drew with her competitors by sending out those passages as excerpts ahead of time. For much of the campaign, Warren has refrained from such direct critiques, but recently she has sharpened her tone.

“Unlike some candidates for the Democratic nomination, I’m not betting my agenda on the naive hope that if Democrats adopt Republican critiques of progressive policies or make vague calls for unity, that somehow the wealthy and well-connected will stand down,” Warren said.

That was aimed at Biden, who stresses his bipartisan bona fides, and Buttigieg, who talks of uniting the country. In a more direct reference to Biden, Warren said, “We know that one Democratic candidate walked into a room of wealthy donors this year to promise that ‘nothing would fundamentally change’ if he’s president.”

Biden made that comment at a New York fundraiser in June as a way of saying wealthy Americans’ lifestyles would not change if they had to pay more in taxes.

Speaking in California, Biden responded to Warren’s criticism without mentioning her by name.

“I read a speech by one of my — good person — one of my opponents, saying that, ‘You know, Biden says we’re going to have to work with Republicans to get stuff passed,’ ” Biden said to chuckles from his audience. “I thought, ‘Well, okay, how are you going to do it, by executive order?’ ”

He added, “This particular person said, ‘He thinks he can actually unify the country — you can’t unify the country.’ Well, guys, if we can’t unify the country, you all ought to go home now.”

Warren called out Buttigieg for naming donors who raise big dollars to a “national investors circle,” saying these contributors get special access to the mayor. “When a candidate brags about how beholden he feels to a group of wealthy investors, our democracy is in serious trouble,” she said.

Buttigieg spokeswoman Lis Smith responded by disparaging Warren’s combative tone. “Warren’s idea of how to defeat Trump is to tell people who don’t support her that they are unwelcome in the fight,” Smith said.

The only rival Warren mentioned directly by name was former New York mayor Mike Bloomberg, one of the country’s wealthiest people. Bloomberg has aired or reserved more than $95 million in broadcast television and radio ads through Dec. 11, according to Advertising Analytics.

She accused him of “trying to buy the Democratic presidential nomination.”

Most of the speech was an attempt to recapture, and refine, her image as an idealist who can get results. As president, she said, she would know how to use the levers of power and would be unafraid to do so.

“Wherever possible, I want to work with Congress on new laws,” Warren said. “But I don’t overlook what’s already available.”

As a reflection of her granular approach, she outlined a litmus test for appointees to the Federal Reserve Board, saying she wants members who “believe in full employment, who recognize that inflation fears have been overblown for years, and who are willing to let wages grow.”

Warren touched briefly on health care, the issue that has tripped her up in recent months as she alternated between a tight embrace of Medicare-for-all and a more phased-in approach.

“My health-care plan delivers the most financial relief, to the most people, more quickly than any plan proposed by any other candidate,” said Warren, adding that her plan would allow about 135 million Americans to participate in Medicare and that others could buy in for what she called “a modest cost.” Warren said she would push for the full-blown Medicare-for-all program in her third year as president.

Warren sought to balance such specifics with an assurance that her goal remains a sweeping overhaul of the system.

“Will we bet on more of the same, or will we bet on change?” Warren said. “Will we bet on small ideas, or will we bet on bold, structural change?”

Michael Scherer contributed to this report.