President Donald Trump escalated a familiar attack on Sen. Elizabeth Warren in early July, mocking the Massachusetts Democrat and leading potential 2020 rival for her claim of Native American heritage.
He revived his nickname for her — "the fake Pocahontas" — and told the crowd at a Montana campaign rally that should the two find themselves on a debate stage, he would challenge her to submit to genetic testing to prove that she has Native American ancestors.
"I will give you a million dollars to your favorite charity, paid for by Trump, if you take the test and it shows you're an Indian," he said. "I have a feeling she will say no."
Warren immediately shot back: "While you obsess over my genes, your Admin is conducting DNA tests on little kids because you ripped them from their mamas," she wrote on Twitter, a reference to the migrant children who have been separated from their parents at the southern border because of a Trump administration policy.
Still, Warren has come under frequent fire — from Trump and others — for her still-unproven claims of Native American heritage.
Here's what we know about her ancestry, what experts say and what a DNA test would show.
How did the debate over Warren's heritage start?
Warren, who grew up in Oklahoma, land that was once Indian Territory, reportedly listed herself in a directory as a minority professor for nine years (from 1986 to 1995) before eventually landing a job at Harvard.
During Warren's hotly contested Senate bid in Massachusetts in 2012, The Boston Herald uncovered a 1996 student newspaper article quoting a Harvard Law School spokesman who boasted that Warren, who was a professor, was Native American. Her campaign scrambled and failed to offer conclusive proof for the claim, which Warren said stemmed from stories her mother told her as a child.
"Being Native American is part of who our family is and I'm glad to tell anyone about that. I am just very proud of it," Warren told reporters at the time.
In a campaign ad, Warren said she had never asked her mom for documentation that her family was part-Cherokee and part-Delaware, but that it was the reason her parents had to elope.
What do her critics say?
Political rivals over the years have attempted to paint Warren as a liar and an opportunist.
"Elizabeth Warren said she was a Native American, a person of color," then-Sen. Scott Brown, R-Mass., said of Warren during one 2012 debate. "As you can see, she's not."
After Warren emerged as a harsh Trump critic during the 2016 presidential campaign, Trump took to calling her "Pocahontas," the name of a storied Native American woman.
"She used the fact that she was Native American to advance her career. Elizabeth Warren is a total fraud. I know it. Other people who work with her know it. Elizabeth Warren is a total fraud," the president told NBC News during his presidential bid.
Would a DNA test prove her claims?
Probably not, and Warren said on NBC News' "Meet the Press" in a March interview she will not take one.
DNA tests are not widely accepted as proof of tribal citizenship — in part because the DNA could not show a specific tribe, only some genetic markers from Native people — and are more unreliable for Native Americans than for large ancestral regions like Asia or Africa.
“The reality is she could take a DNA test and have Native ancestry and have it not show up because it depends on which branches of the family tree it’s in and how far back,” independent genealogist Megan Smolenyak Smolenyak said. “That test is very good for finding stuff out going back five, six generations. If you have one great-great-great-great-grant-great grandmother, it’s not going to show.”
What do historians and genealogists say?
Native Americans are still the second-largest minority group in Oklahoma, according to the 2010 Census, and tales of Native ancestry are common, experts said.
"My family has a narrative that we're Choctaw, but we don’t have any proof of that," Larry O'Dell, the Oklahoma Historical Society's director of special projects and development, said when asked about tracing Native heritage. "My boss and I were talking earlier, and he has the same kind of narrative. It's just sort of the way it is in Oklahoma."
Smolenyak, who has traced former first lady Michelle Obama's family back to slaves and former President Barack Obama's ancestors to Ireland, said one of the biggest myths in genealogy is how many families believe their ancestor was a Cherokee princess.
"It's always Cherokee, and it's always a princess," she said.
More than 819,000 people told the 2010 Census they are at least part Cherokee, despite the nation’s three federally recognized Cherokee tribes only having half as many members.
Laura Martin, a deputy director for the Oklahoma Historical Society's research division, said 98 percent of visitors to their library are hunting down ties to Native American heritage. But in order to obtain documentation that's registered by tribes or the U.S. government, ancestors must be listed on historical registers like the Dawes Rolls, which the federal government used to distribute communal tribal land to individual Indians who enrolled between 1898–1906.
"We can help you find federal Census records, marriage records, death records, things like that, but if they did not sign up [on official documents], it kind of ends there," Martin said.
Did her self-identified minority status help her career?
Warren has adamantly insisted that she never used her heritage to get ahead, and there’s no evidence that it was a deciding factor in her employment at Harvard.
The Boston Globe published an exhaustive investigation in September that included a review of university personnel files — first released to the paper by the senator — and more than 100 interviews with colleagues and every individual who played a role in hiring decisions about Warren who could be reached.
The paper reviewed a University of Pennsylvania document that shows Warren was viewed as a white woman by those who chose to employ her; the hiring committee explains its decision to hire her — over minority candidates — in some length on the form. At Harvard, a human resources form shows that Warren first listed herself as Native American five months after making tenure.
"In sum, it is clear that Warren was viewed as a white woman by the hiring committees at every institution that employed her," the newspaper concluded.
So, is Warren actually Native American?
There is no documented proof that Warren is descended from Native Americans.
Warren has not provided any. Genealogists who have investigated her history have found her relatives to be listed as white in historical documents like the Census and do not appear in the Indian documents typically used to verify claims of Native American ancestry, like the Dawes Rolls.
The New England Historic Genealogical Society initially said they had proof that she was 1/32nd Native American, only to later backtrack and say they did not have definitive proof. They declined to comment for this story.
Cherokee genealogist Twila Barnes traced Warren's maternal family back four generations to the turn of the 19th century; the records listed all members as white. She could not find Warren’s family in any of the 45 Indian records and documents she reviewed for a detailed report.
This doesn't mean that Warren is not Native American — some Native Americans were not listed in the Dawes Rolls, for instance, or her ancestors could be from well before those records — but it does mean that there is no evidence that she is, either.
Accordingly, she would not be eligible for citizenship in Indian tribes like Cherokee Nation, as they commonly require a direct ancestor to be listed on those records.
"The fact that it hasn’t been substantiated doesn't 100 percent mean it won't be substantiated," Smolenyak told NBC News, six years after she first started looking into Warren's family. "But … you would have hoped for some proof within this time frame."
Warren, in a speech this year to a Native American group, addressed the controversy and said she stands by the stories she was told as a child.
"I get why some people think there's hay to be made here. You won’t find my family members on any rolls, and I'm not enrolled in a tribe," she said. But, she added, "my parents were real people."