The exchange marks the first time Warren has hit back directly at Buttigieg after months of simmering tensions that started when he called her “extremely evasive” on her plan for Medicare for All. It signals a strategic departure for Warren, who has largely avoided criticizing her rivals or their policies, even when they have accused her of “elitism” or suggested she is too divisive to win.

But this week, the Massachusetts senator showed a new willingness to counterpunch, and her first target was a candidate who preaches about the need for unity: Pete Buttigieg, the young mayor of South Bend, Ind., who is rising in the polls after excoriating Warren’s health care plan.

Though she seems to promise a fight at every turn, Elizabeth Warren has mostly refrained from attacking her fellow Democratic presidential candidates.


Speaking to reporters in Boston on Thursday night, Warren called Buttigieg out for his use of the traditional private fund-raisers that attract high-rollers and access-seekers, events she has sworn off for her presidential run.

“Mayor Pete should open up the doors so that anyone can come in and report on what’s being said,” Warren said. “No one should be left to wonder what kind of promises are being made to the people who have been ponying up big bucks to be in the room.”

Buttigieg’s campaign immediately hit back, calling for Warren to release additional information on her finances, beyond the 11 years of tax returns she has already posted online — specifically records of her early years of freelance corporate law work. And on Friday, Buttigieg himself suggested Warren had flip-flopped on the campaign finance issue, because she attended exclusive fund-raisers when she was running for the Senate.

“She was for it before she was against it,” he said in an interview with ABC.


The sparring between Warren and Buttigieg is at odds with what had drawn so many early-state voters to hear them make their pitches. Many of these voters say they like both politicians and don’t want the primary to devolve into a mudfight. Crowding into a high school gym where Buttigieg spoke on Thursday, several voters said they were torn between the two candidates, who both disproportionately attract white, educated liberals.

“I just love listening to him talk. I think people don’t clap because we don’t want him to stop talking,” said Lee resident Lori Rainey, 62. “We’re all very hungry for a leader we can trust.”

But Rainey said she is also impressed by Warren. “I think she’s tough and I think she could hold her own against” President Trump, she said.

Warren’s willingness to tangle comes as her polling numbers slip, and appears to be part of a broader effort to shift her campaign strategy.

Although her shot at Buttigieg paled in comparison to criticism she has received from him and other rivals, it carries risk because her reluctance to engage in infighting has won plaudits from voters who say they don’t want to see Democrats squabbling.

“I think it’s time to stand by your policies, not necessarily attack the policies of others,” said Mark Fuller, 36, a community college worker who wore a T-shirt emblazoned with photos of Warren to a campaign event in Marion, Iowa, on Sunday.

“At the end of the day, we’re going to fall in love now” with voters’ first choices, Fuller said, “and then we need to fall in line once we get a candidate.”


But with Buttigieg rising in Iowa, Warren and her campaign team have apparently calculated that the time has come to stoke doubts about the 37-year-old mayor. In a poll of Iowa voters released last month by the Des Moines Register, Buttigieg shot up 16 percentage points while Warren slid by 6.

“She’s really in a difficult spot here. She doesn’t really have a choice but to do that, but if she goes too far, that’s just going to hurt her even more,” said Dave Degner, chairman of the Tama County Democrats in Iowa, who is leaning toward Buttigieg among several candidates.

Warren’s criticism of Buttigieg does not necessarily mean she will stay on the attack. Her remark fell within a central theme of her campaign: battling “corruption” in politics that makes politicians beholden to the wealthy and special interests who fund their campaigns. And she has been willing to take occasional shots at rivals in the past, once saying Joe Biden was “running in the wrong primary” when he criticized her Medicare for All plan, and accusing billionaire rivals Michael Bloomberg and Tom Steyer of trying to buy the election.

The risks of going on the attack have not been distributed equally. After the first debate, Senator Kamala Harris of California seemed momentarily to deflate Biden’s presidential ambitions when she condemned his opposition to federally mandated busing. She was criticized for the attack in the following days and dropped out of the race this week.


Yet Buttigieg began to dig out of a polling slump after attacking Warren earlier this fall. During a debate in October, he accused her — accurately — of failing to explain how she would pay for Medicare for All.

And when Warren released that plan, he questioned her math. He has also suggested numerous times that for Warren, who has engaged in high-profile clashes with Trump and members of the Obama administration, “fighting is the point,” and contrasted that with his own message of unity.

This week, his campaign was a split screen. In New Hampshire, he talked about the importance of hope, and the need to bring the country together and foster a sense of belonging as president.

But off the stump, he tussled with Warren, as well as with Bernie Sanders, getting into a back-and-forth with the Vermont senator over his free-college-for-all plan. “Rich people ought to pay their own tuition,” Buttigieg told reporters Monday, adding that some candidates’ plans ignore “the fact that not everybody goes to college.” Sanders said Buttigieg was “wrong” in an interview on MSNBC.

Even his own fans suggest Buttigieg’s attacks come at his own peril.

“The one thing I caution against for any of these candidates is they need to resist the circular firing squad, and I do think that’s what has done in a couple of people, Kamala [Harris] in particular,” said Liz Gilmore, 76, who watched Buttigieg speak in Henniker, N.H., on Thursday.


“I want him to resist,” she said.

Jess Bidgood can be reached at Jess.Bidgood@globe.com. Liz Goodwin can be reached at elizabeth.goodwin@globe.com.