In a direct response to President Donald Trump’s taunts, Sen. Elizabeth Warren revealed on Monday that a DNA test provides compelling evidence that she does, in fact, have Native American ancestry.

Warren announced the test results in a highly produced biographical video that looks like the opening salvo in a campaign against Trump for the presidency, which the Massachusetts senator said last month she would “take a hard look at” pursuing after her likely re-election in November.

The video, which points to a new section of the Massachusetts Democrat’s website dedicated to facts about her heritage, begins with images of the senator returning to meet her brothers in Norman, Oklahoma, where she was raised, as audio of Trump mocking her as a “fake Pocahontas” rings out on the soundtrack.

Clips of Trump and other Republicans deriding Warren for what they assumed was her false claim about her Native ancestry are interwoven with the senator and her brothers recounting family lore about Native roots, which appears to trace their ancestry back to a great-great-great-grandmother, O.C. Sarah Smith, once described as Cherokee.

Warren is then shown getting the test results from Carlos Bustamante, a professor of biomedical data science, genetics, and biology at Stanford University, who has advised the genetic testing services Ancestry.com and 23andMe, as well as the PBS series “Finding Your Roots.”

“The president likes to call my mom a liar,” Warren tells Bustamante. “What do the facts say?”

“The facts suggest that you absolutely have a Native American ancestor in your pedigree,” Bustamante replies.

“In the senator’s genome,” Bustamante explains to the video crew, “we did find five segments of Native American ancestry with very high confidence, where we believe the error rate is less than 1 in a 1,000.”

A copy of the full report from Bustamante’s lab, posted online by the Boston Globe, makes it clear that the “identity of the sample donor, Elizabeth Warren, was not known to the analyst during the time the work was performed.”

“My family (including Fox News-watchers) sat together and talked about what they think of @realDonaldTrump’s attacks on our heritage,” Warren wrote on Twitter Monday morning. “And yes, a famous geneticist analyzed my DNA and concluded that it contains Native American ancestry.”

The video also sets out to debunk the false claim that Warren had gained a professional advantage in her previous career as a law professor by identifying herself as part Native American. A series of law school administrators and professors who took part in her hiring repeatedly dismiss that claim as nonsense. Last month, the group spoke to the Boston Globe, which was given access to Warren’s personnel files, for a debunking of the falsehood.

Warren also pointed to that evidence on Twitter, in a thread encouraging readers to “review every document for yourself.”

News of the DNA test, and the video, was first provided by Warren’s office to the Boston Globe reporter Annie Linskey, who described it as evidence that the senator, if she runs for president, “plans to be a very different candidate than Hillary Clinton was.”

“The 2016 Democratic nominee for president,” Linskey wrote, “chafed at releasing personal information and was dogged throughout her campaign by her use of a private server while she was secretary of state.”

The campaign-style video, raising and debunking attacks on her, could also be seen as evidence that Warren has learned the lessons of another failed Democratic nominee: John Kerry, who refused to aggressively confront false claims about his service in Vietnam that were raised by an outside group, Swift Boat Veterans for Truth, in 2004.

Linskey’s report, which features a more extensive interview with Bustamante, notes that the genetic expert estimated that Warren’s Native American ancestor appears in her family tree “in the range of 6-10 generations ago.” That would seem to fit the story that Warren’s parents told their children about their maternal great-great-great-grandmother.

However, the Boston Globe report could also point to ways the story might soon be attacked by Warren’s political opponents, as they seek to cast doubt on the results. Bustamante was careful to say that his lab is “confident it is not an error” to say Warren has Native American ancestry, but the imprecision of genetic testing will no doubt soon be a subject of national debate should the senator run for president.

As Linskey explains, Bustamante was also forced to use a creative method to identify Native American genetic material, which could give Trump supporters an opportunity to dispute the findings:

Detecting DNA for Native Americans is particularly tricky because there is an absence of Native American DNA available for comparison. This is in part because Native American leaders have asked tribal members not to participate in genetic databases.

“The tribes have felt they have been exploited,” explained Lawrence Brody, a senior investigator with the Medical Genomics and Metabolic Genetics Branch at the National Institutes of Health. “The amount of genetic data that is available from Native Americans is sparse.”

To make up for the dearth of Native American DNA, Bustamante used samples from Mexico, Peru, and Colombia to stand in for Native American. That’s because scientists believe that the groups Americans refer to as Native American came to this land via the Bering Straight about 12,000 years ago and settled in what’s now America but also migrated further south. His report explained that the use of reference populations whose genetic material has been fully sequenced was designed “for maximal accuracy.”

Bustamante said he can tease out the markers that these South Americans would have in common with Native Americans on the North American continent.

Despite a total lack of evidence, Trump’s attacks on Warren have already convinced millions of his supporters that she somehow gained an unfair advantage through the affirmative action programs they despise. If Warren declares her candidacy in the months ahead, expect to hear a lot about the fact that Bustamante’s lauded work on genetics has focused, in part, on what his lab’s website describes as “broadening representation of understudied groups, particularly U.S. minority populations and those from Latin America” and “calling attention to the problem raised by >95% of participants in large-scale studies being of European descent.”

Quite apart from the implications for electoral politics, the news of Warren’s DNA test struck several Native American observers as problematic for the assumptions about identity, race and belonging that it revealed.

Warren’s claim to Native American identity based on such remote ancestry has prompted criticism from other activists in the past.

As news of the test results spread on Monday, Warren also reminded Trump of his promise at a rally on July 5 that he would donate $1 million to a charity of her choice if she took a DNA test that supported her claim to Native American ancestry.

When a reporter tried to ask Trump on Monday if he would now make the donation, the president cut him off and denied ever making such a promise, even though he made it just three months ago, during a televised rally.

Just 90 minutes later, Warren’s team used video of Trump’s denial in a new attack ad posted on social networks, with the prominent caption: “This is what lying looks like.”

Updated: Oct. 15, 1:21 p.m. EDT
This report was updated with reaction from some Native American writers and the video of Elizabeth Warren’s attack ad criticizing Donald Trump for refusing to donate money to a charity of her choice after she took a DNA test to offer evidence of Native American ancestry.

Top photo: Sen. Elizabeth Warren at a campaign rally in Sept. 2018, in Cambridge, Massachusetts.