The direct engagement with Buttigieg and Biden is part of a tactical shift for Warren in recent weeks that also includes a more aggressive appeal to female voters, and a revised stump speech. The changes come as Warren has stalled or dipped in national and early-state polls heading toward a decisive month of campaigning before the Feb. 3 Iowa caucus.

The Massachusetts senator had resisted engaging her Democratic rivals directly, preferring to try to deflect their attacks rather than counter-punch. She and her campaign worried that hitting other Democratic hopefuls would repel voters and make them unlikely to ever support her.

The campaign felt validated in that approach even in the face of attacks from fellow rivals, given that Warren is usually the second choice among supporters of other candidates. But as she tries to regain her momentum from the summer and early fall, Warren has stepped up her criticism of other top Democrats.

The campaign openly derides what they call the “pollercoaster” of narratives driven by public polling, but the shifts amount to acknowledgment that Warren felt she needed to change her approach in the final stretch before the first nominating contests. Her detailed policy plans have not made as much news or driven the debate the way they did earlier in the campaign. And her straddling between the center and the left on Medicare for All has kept her off balance for months.

Warren did not name her rivals in the speech, but she left no room for interpretation. Pointing to Biden telling attendees at one fundraiser that “nothing would fundamentally change,” and to Buttigieg launching a “National Investors Circle” for people who pledge to raise over $250,000 for his campaign, she argued they're supporting an inherently corrupt system.

“When a candidate brags about how beholden he feels to a group of wealthy investors, our democracy is in serious trouble,” Warren argued.

Biden’s campaign declined to comment but the former vice president has responded to similar criticism from others. At a September fundraiser in Chicago , he told the audience, “Here’s what I’m not naive about. Unless we figure out how to unite the country, none of this works. None of this works.”

Lis Smith, a senior adviser to Buttigieg, hit back at Warren in a statement. “Senator Warren's idea of how to defeat Donald Trump is to tell people who don’t support her that they are unwelcome in the fight and that those who disagree with her belong in the other party," Smith said. "We need to move beyond the politics and divisiveness that is tearing this country apart and holding us back. Pete will be a President who will heal our divides and rally Americans around big ideas to solve the problems that have festered in Washington for too long."

Warren’s speech was a continuation of the more direct attacks she began deploying last week when she called on Buttigieg to open his fundraisers to the media and release his clients from his time working at the management consulting firm McKinsey. Buttigieg responded by calling Warren to release financial records from her time representing corporations as a lawyer. Ultimately, both bowed to the calls for greater transparency.

Warren has also deployed a new, shorter stump speech. It includes sections from her October speech at Iowa’s Liberty and Justice dinner, along with a clearer call for her Medicare for All plan, after facing skepticism from the left about her commitment to the issue. The slimmed-down format also allows more time for audience questions, which the campaign films with the hope of a viral moment.

And she has been making more open appeals to women voters in an attempt to tap into the energy that drove the Women’s March in 2017 and led to a record number of victories for female candidates in the 2018 midterms. Warren recently announced that its campaign co-chairs would all be female congresswomen elected in that 2018 wave: Reps. Ayanna Pressley, Katie Porter, and Deb Haaland.

The campaign has also been running several Facebook ads pushing “Women with Warren” campaign gear and bemoaning the early exits of Sens. Kamala Harris and Kirsten Gillibrand from the presidential campaign.

And in another recent move, Warren has used former New York City Mayor Michael Bloomberg as a foil since he joined the 2020 race.

“It’s no secret that I’m not a fan of Michael Bloomberg trying to buy the Democratic presidential nomination,” she said Thursday.