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Elizabeth Warren has managed to largely avoid conflict with her Democratic primary rivals while rising steadily in the polls — so much so that now, multiple candidates are seeking to wrangle with the senator from Massachusetts.

Interviews with senior campaign staff of four rival campaigns reveal a clear desire to increase voter scrutiny of Warren and her record, and remarkably similar game plans of how to do it.

They argue that she has been given a pass for much of the year, with her professional and political history receiving less scrutiny than other candidates. They also argue that the divisive impacts of some of her policy proposals, including Medicare-for-all — which she supports along with Sen. Bernie Sanders (I-Vt.) — have not yet been fully presented to the party’s voters.

Former vice president Joe Biden, for one, prepared more zingers for Warren at the last debate than he was able to deliver onstage. So a day later, at a fundraiser in a wealthy Houston neighborhood, he decided to let fly.

“We need more than plans. We need a president,” he said, referring to the policy-heavy campaign of the senator from Massachusetts. He also joked about how “half the people” on the debate stage were Republicans back in 1972. In fact, there was only one, Warren, who has said she identified as a Republican or independent before 1996.

Days after the debate, South Bend, Ind., Mayor Pete Buttigieg, who is trying to reposition himself in the race, became the second candidate to go public with an attack on Warren, arguing in television interviews and in a Facebook ad that the “Sanders-Warren vision” for health care would polarize the country, not bring it together. Sen. Michael F. Bennet (Colo.) has also purchased more than $1 million in ads in Iowa arguing against Medicare-for-all, including one spot that argues the plan will “blow up everything.”

But the broader unfolding critique against Warren attempts to raise deeper questions about how she presents herself. Advisers to some rival campaigns point to her past identification as a Republican and her corporate consulting work on bankruptcy cases. They also note her record of soliciting donations from wealthy individuals, including lobbyists, before deciding to stop taking lobbyists’ money and, earlier this year, to cease major fundraising events.

Warren’s team has refused to be swayed by such taunts. Warren, a former statewide high school debate champion, has ably defused confrontation in the first three debates, repeatedly returning to her central message, which is that she is a fighter ready to confront political and economic elites who are responsible for middle-class struggles. It’s a message that has attracted a significant following, as demonstrated by a 20,000-person rally Monday night in Manhattan.

“We will continue to run the campaign we have from the beginning — identifying what is broken, talking about our plans to fix it, and building a grass-roots movement to make it happen,” Warren communications director Kristin Orthman said in response to the attacks.

Biden at the helm

Biden, who continues to lead in national and early state polls, has been leading the new critique of Warren by raising questions about her “candor,” with a focus on her refusal to describe the details of Medicare-for-all. His campaign previewed the last debate by boasting that he was the only candidate who had released 20 years of tax returns — an oblique reference to Warren, who has released 11 years of returns, not including years when she did the bulk of her corporate legal work.

Unlike Sanders, who has admitted that the health insurance program would raise middle- class taxes while aiming to reduce total costs, Warren has refused to answer the question about whether Medicare-for-all would raise middle-class taxes. She has described the question as missing the point, saying total cost is all that matters for struggling families.

“When you’re not candid about what you’re going to do, it makes it very difficult,” Biden told reporters Friday.

Warren has argued that the corporate work she did while serving as a law professor — for clients such as Dow Chemical and Travelers Insurance — was focused on helping “victims hurt by bankrupt companies,” including asbestos claimants and women with breast implants that could rupture. In May, she disclosed a list of about 60 legal matters that she worked on, including many that were not previously known.

Hedging their bets

The decision to go after Warren more directly carries clear risks for her rivals. The first months of the Democratic primary have been littered with candidates who became casualties of their own offensives, which Democratic voters tend to recoil from, especially in early voting states such as Iowa.

Sen. Kamala D. Harris (Calif.) faded in polls after a brief spike following a fierce critique of Biden on school segregation policy in the June debate. Former U.S. housing secretary Julián Castro found himself on defense after inaccurately suggesting at the last debate that Biden, 76, had forgotten what he had said a few minutes earlier. Two others, Sen. Kirsten Gillibrand (N.Y.) and Rep. Eric Swalwell (Calif.), left the race shortly after using their prime-time debate time to attack Biden directly.

But Warren’s rivals also feel there is a potentially greater cost to letting Warren continue her campaign without more scrutiny, after showing herself to be the only candidate in the race who has been gaining strength for much of the year.

“If you look at Biden, for example, he has taken incoming essentially every day of the campaign since he got in — frankly since before he got in — and his support hasn’t moved. I think it is an open question what happens to her support when she starts taking incoming as well,” said one Democrat affiliated with a rival campaign, who like several others spoke on the condition of anonymity to discuss campaign messaging strategy.

“She hasn’t been tested in the same way.”

Advisers to two other campaigns said the policy approach of Warren, which is focused on what she calls “big structural change,” probably would foreclose the possibility of bringing the country together after the Trump administration. “If people are tired of war all the time in our country and a press who is fomenting those divides, how is a progressive overhaul of the whole country going to answer to that?” asked an adviser for a second campaign in describing how she could be challenged.

What Republicans are thinking

The Democratic questions about Warren’s candor echo a separate line of argument that has been developed by Trump and his Republican allies in case Warren wins the nomination. The Republican National Committee regularly calls her a “fraud,” and Trump has attempted to use Warren’s past identification as a Native American as evidence that she is not who she presents herself to be.

Former Republican political strategist Steve Schmidt, who served as Sen. John McCain of Arizona’s 2008 campaign manager and left the Republican Party because of Trump, said that Warren’s vulnerability on this score will be tested if she makes it to the general election.

While liberals dismiss the president’s “Pocahontas” nickname for Warren as a racist slur, Schmidt said that many voters probably will hear in it a reminder of the allegation that Warren tried to game the system in academia, although those involved in her hirings say it did not play a role. While he called Trump “the most prolific liar that has ever run for office,” Schmidt said Trump had also proudly described his own efforts to find personal advantage in his private life, like his efforts to reduce his own tax bill.

“There is no artifice,” Schmidt said of Trump. “Any candidate that gets into a quagmire around honesty issues with Trump is going to be a defeated candidate.”

Sanders vs. Warren

So far, Warren has not had to worry about attacks from the other leading candidate in the race pushing for dramatic policy change. Sanders and Warren have refrained from challenging each other publicly, and Warren has repeatedly praised his ideas. But there are some staff-level tensions below the surface, as Sanders advisers seek to draw electability comparisons with Warren.

In a Tuesday email to supporters, Sanders aides pointed to some recent polls showing his leads over both Biden and Warren in support among working-class white and Latino supporters. An NBC-Wall Street Journal poll on Tuesday showed Warren slightly edging Sanders and Biden among Latinos, and polling higher than Sanders among whites without a college degree.

Sanders has also not held back from competing for the same voters Warren seeks. He plans to hold a rally Sunday in Norman, Okla., Warren’s birthplace, and one of the few states that will vote in the early spring that she has yet to visit as part of her campaign.

The Sanders campaign has distinguished itself by eagerly pushing back against Biden’s attacks on Medicare-for-all. Sanders’s campaign manager, Faiz Shakir, called Biden “Pinocchio Joe” on Twitter on Tuesday, after Biden claimed at a union event that he had always supported union causes. Another adviser called Biden “the senator from MBNA,” a reference to a prominent Delaware bank.

Aides to Warren, meanwhile, devoted their Twitter accounts to carrying their candidate’s message — boasting about the four hours Warren had spent taking photos with supporters after her Monday rally in New York.

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