With two of the least popular nominees in history representing the major parties in the presidential election, third parties see an unprecedented opening. That’s certainly the case for Green Party candidate Jill Stein, who’s making a play for Sen. Bernie Sanders’ most passionate supporters who refuse to back Hillary Clinton.

While Stein’s sensibilities carry serious appeal for disillusioned liberal voters, there’s one issue that has dogged her campaign from the start: claims that Stein is a so-called “anti-vaxxer.” But the Harvard-educated physician, faced with her best chance to capture mainstream appeal, has failed to forcefully reject anti-vaccine arguments, which have been disproven by a wealth of scientific research.

Stein didn’t do much to help her cause when given the chance to clarify her stance in a Green Party town hall hosted by CNN on Wednesday night. While declaring vaccines a public health necessity, she also effectively echoed the “just asking questions” talking point used by leaders of the anti-vaccine movement.

“I think there’s kind of an effort to divert the conversation from our actual agenda. The idea that I oppose vaccines is completely ridiculous, or that I’m anti-science,” Stein replied.

She directed viewers to read two of the scientific papers she co-authored, saying, “I am certainly not hostile to science or anti-science.”

She also said her remarks on concerns about the childhood immunization schedule date back to when she was still practicing and closely following developments in medical research.

“When I was practicing and following issues of immunization, which I am not now, there were concerns at the time about the mercury dose in vaccinations and how kids might be loaded up in a way related to that schedule and the presence of thimerosal in the vaccines,” Stein said.

There were “legitimate questions at the time” about the use of the chemical thimerosal, she continued, saying, “But I understand that the thimerosal has been taken out of the vaccines and it’s no longer an issue.”

Stein’s side-stepping of the thimerosal issue should raise eyebrows.

Thimerosal, an organic chemical compound that contains mercury, was used as preservative in immunization, but anti-vaccination activists have long insisted that a link exists between thimerosal and rates of autism. No such link has been proven, and the 1998 study that aroused anti-vaxxer’s suspicions was later retracted, with its author now banned from practicing medicine.

“For policy wonks, for science geeks, you can show yourself if you have any doubt, that I too am a science geek,” Stein continued. “I believe that asking questions is part of our responsibility as scientists and as physicians. We always need to be asking those questions.”

Stein also had touched on the “questions” she believes linger around vaccines in an interview with the Washington Post late last month, allowing some space for scientific uncertainty.

“As a medical doctor, there was a time where I looked very closely at those issues, and not all those issues were completely resolved,” she told the Post. “There were concerns among physicians about what the vaccination schedule meant, the toxic substances like mercury which used to be rampant in vaccines. There were real questions that needed to be addressed. I think some of them at least have been addressed. I don’t know if all of them have been addressed.”

Although she went on to say we have a “real compelling need for vaccinations,” Stein also said regulators at the Food and Drug Administration and the Centers for Disease Control and Prevention are ruled by “corporate influence” and outsized influence by the pharmaceutical industry.

That’s another concern often raised by the anti-vaxxer crowd: that corporation-stacked regulatory bodies are showing unsafe or untested vaccines through to market. But as the Post points out, 11 of the 15 members of the FDA’s advisory committee on vaccines are employed by academic and medical institutions, not Big Pharma. Two committee members work at pharmaceutical companies and two other seats remain vacant.

Stein made similar remarks in a much-criticized Reddit AMA in May. Stein hedged that “vaccines in general have made a huge contribution to public health” but that “the foxes are guarding the chicken cook,” with regulatory bodies that are “routinely packed with corporate lobbyists and CEOs.”

“So who wouldn’t be skeptical? I think dropping vaccinations rates that can and must be fixed in order to get at the vaccination issue: the widespread distrust of the medical-industrial complex,” Stein wrote. “Vaccines should be treated like any medical procedure. Each one needs to be tested and regulated by parties that do not have a financial interest in them.”

At the height of criticism against her comments on vaccines earlier this month, Stein’s campaign put out a statement saying the “baseless” attacks to smear her as “anti-science” were akin to the birther controversy with President Barack Obama.

“Anyone who supports vaccinations and wishes to prevent dropping vaccination rates should be concerned about the erosion of public trust caused by the corrupting influence of the pharmaceutical industry in regulatory agencies and government in general,” Stein said in the statement.