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Elizabeth Warren rebuts Trump’s “Pocahantas” attack with DNA evidence.

Even before he became president, Donald Trump has attacked the Massachusetts senator over her belief, via family lore, that she has Cherokee ancestry. He has repeatedly called her “Pocahontas,” including at an event honoring Navajo code talkers. For Trump, Warren’s claims are proof that she’s a phony, even though it was made clear back in 2012 that Warren had never used any claim about her heritage to advance her career.

On Monday, Warren, a likely 2020 presidential candidate, released a video about her Native American ancestry that included DNA evidence that suggests distant Cherokee heritage.

The video is calibrated to undercut Trump’s criticisms. “The president likes to call my mom a liar—what do the facts say?” Warren asks Stanford University Professor Carlos Bustamante, a geneticist who conducted the DNA analysis. Bustamante responds that the results “strongly suggest” Native American heritage. The video also features Warren discussing the president’s criticisms with her family in Oklahoma, where she is originally from. Relatives, including registered Republicans, dismiss it as “ridiculous,” a “bunch of crap,” and a personal slight against Native Americans and Warren’s mother.

The aim of the advertisement is twofold. First, it strives to undercut the “Pocahontas” attack. Republicans had long demanded that Warren take a DNA test to prove that she was Native American. That attack was always made in bad faith—particularly the baseless claim that Warren used her heritage for career advancement—and Republicans aren’t likely to give it up. But second, it ties Warren to the working-class Oklahoma roots one can expect her to lean on in a presidential race.