DES MOINES, Iowa (AP) — Elizabeth Warren is fighting to regain momentum in the turbulent tussle for the Democratic presidential nomination amid lingering questions about her consistency and ability to defeat President Donald Trump.

Warren was considered a leader in the crowded race through the fall, yet just days before Iowa’s first-in-the-nation caucuses, allies, adversaries and new polling suggest that progressive rival Sen. Bernie Sanders has a slight advantage — at least in the battle for the party’s left wing. That’s just as establishment-minded Democrats begin to rally behind former Vice President Joe Biden, who has tried to stoke fears about his more liberal rivals’ ability to win in November.

Warren’s uncertain status raises questions about whether any female candidate will emerge from Iowa’s Feb. 3 caucuses with the political strength to go deep into the primary season, a challenge that will almost certainly require early victories to generate the energy and campaign cash needed to continue.

As would-be supporters acknowledged concern over the weekend, Warren ignored the shifting political currents and vowed to continue fighting for the kind of transformational change she’s championed for months, even while pressing her final case in Iowa before being forced back to Washington for Trump’s impeachment trial in the Senate.

“Since I first got in this race a year ago, I have not focused on polls. And that’s exactly how I’m going to continue to run this race,” Warren told reporters when pressed about whether she needs to change her strategy.

She added: “I’m running a campaign from the heart. That’s what it’s all about to me. This is who I am.”

The people paid to focus on politics on Warren’s team insist they’re not worried, and with one week before voting begins, there are no plans to shake up her strategy. The campaign noted that she has already attracted more than 3 million individual donations and assembled a paid campaign operation in 31 states.

The 70-year-old Massachusetts senator got a much-needed boost over the weekend by winning the endorsement of Iowa’s largest newspaper. And while she has won a series of coveted newspaper endorsements, Warren has yet to earn the backing of a single member of Congress from Iowa or New Hampshire, the states that host the first two voting contests.

The shutout particularly stings given Warren’s proximity to New Hampshire, whose two female senators have declined to support their neighbor, who has increasingly evoked her gender as a strength on the campaign trail.

New Hampshire Sen. Maggie Hassan is unlikely to support Warren and is instead considering whether to endorse longtime political ally Biden, if anyone, according to Democrats familiar with her thinking who were not authorized to share internal discussions. New Hampshire’s other senator, Jeanne Shaheen, is facing reelection this fall and is not expected to endorse anyone.

Meanwhile, Biden was campaigning alongside his newest high-profile female supporter, Iowa Rep. Cindy Axne, as he worked his way across Iowa over the weekend. Biden has won the public backing of both of Iowa’s Democratic congresswomen.

Warren’s allies believe she will benefit from her sprawling organization of paid staff and volunteers on the ground in Iowa and other early voting states in addition to an aggressive paid advertising campaign. She’s also expected to earn a wave of new endorsements from local progressive leaders on Monday as her allies work to spark a final-week surge.

The Warren-aligned Progressive Change Campaign Committee, the Working Families Party and Black Womxn are set to announce more than 3,000 new endorsements for Warren including elected officials, economists, organization leaders, small business owners and activists, according to PCCC co-founder Adam Green. That’s in addition to the endorsement of more than 40 Iowa Democratic officials and activists, the campaign announced on Sunday.

But sensing weakness, Warren’s rivals are actively working to peel off her supporters.

Sen. Amy Klobuchar of Minnesota, one of the two other women in the race, sees Warren as one of her best targets as she fights to bump off one of the top four candidates. As Warren allies cheered her Des Moines Register endorsement, Klobuchar’s team touted her endorsement from another one of the state’s largest newspapers, the Quad City Times.

Iowa Democrat Deidre DeJear, who served as Kamala Harris’ state chair before the California senator left the race, acknowledged Warren’s uncertain status.

“I think there has been some stagnation,” DeJear said of Warren’s support. “I don’t think that she’s struggling by any stretch of the imagination, but I believe as it relates to people’s temperature, poll numbers, folks have either made another decision or we’re not necessarily seeing her support represented in the polls.”

The rivalry between the Democratic Party’s most liberal contenders, Warren and Sanders, looms largest as voters finalize their decisions. And in the fight for the left, a series of state and national polls over the weekend suggest Sanders is better positioned than Warren on the eve of the first voting contest.

A New York Times/Siena College poll released Saturday showed Sanders with a slight edge in Iowa, though polls also show that all four top candidates remain in the hunt there. In New Hampshire, several recent polls put Sanders out front, with Warren and the other top candidates lagging behind. And two polls released Sunday suggest that Warren is running well behind Biden and Sanders nationally.

Undecided Iowa voter Tyler Niska says he’s narrowed his choices to Sanders or Warren, yet he fears that Warren would face the same political headwinds that plagued the party’s last female nominee, Hillary Clinton, four years ago.

“Warren would probably do a better job, but Bernie has a much better chance of actually winning,” Niska, a 36-year-old Des Moines resident, said as he waited in line outside a weekend Sanders rally in Ames.

“I’ll probably go with Bernie,” he said.

Progressive voters interviewed in recent days raised questions about Warren’s ability to win the general election. They also expressed concerns about her authenticity, an issue that they say stems stems from her shift on “Medicare For All,” a core priority for many liberal activists that Warren now says she would wait as long as three years to implement if elected.

Peter Murphy, a 70-year-old from small-town Marshalltown, said he considered supporting Warren but decided that Sanders, of Vermont, was more consistent in defending progressive values.

“I liked what she said at one time. I still think she’s OK,” Murphy said. “She says a lot of what he says. He has been saying it longer.”

And David Riley Campbell, a 23-year-old who has been volunteering for Sanders, said he likes Warren but “she doesn’t quite go far enough.”

“She’s been shifting her positions,” he said, pointing to Medicare For All.

Warren volunteer Amber Beitzel, of Bettendorf, said she’s aware of recent polls showing Sanders with an advantage and said it’s something to watch. But she’s seen Warren’s operation up close and feels it’s well positioned.

“There’s a concern, obviously,” said Beitzel, 38, who works in nuclear medicine technology. “But I feel like working in her grassroots campaign, I see her organizers, I see the volunteers come. … They’re coming back with lots and lots of people who are interested in what she’s saying. And it’s very exciting.”

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AP polling director Emily Swanson in Washington and AP writer Hunter Woodall in Manchester, New Hampshire contributed.

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