Ms. Warren, Democrat of Massachusetts and a former professor at Harvard Law School, listed herself as a member of a minority group in a law school directory but has not claimed to be a Native American since being elected to the Senate in 2012.
Beyond Mr. Trump’s ridicule, some American Indian activists have pressured Ms. Warren to be more straightforward about her heritage and to also be a more aggressive advocate for the tribes, some of which account for the most impoverished communities in the country.
Such demands, combined with the attention that Mr. Trump commands with his mockery, prompted her to try to engage in what one supporter of hers allowed was something of a deck-clearing going into her expected re-election in November and before a Democratic primary race that will effectively start at the end of the year.
To that end, Ms. Warren, an Oklahoma native, used a recounting of her roots to not just tell her family’s ethnic story but to present a tale of Dust Bowl hardship that has the makings of a stump speech aimed at inoculating her against charges of being a member of the coastal elite.
“My mother’s family was part Native American,” she said on what would have been her mom’s 106th birthday. “And my daddy’s parents were bitterly opposed to their relationship. So, in 1932, when Mother was 19 and Daddy had just turned 20, they eloped.”
She recalled how, after her father had a heart attack and lost his job, her mother “put on her best dress and walked to the Sears and got a minimum-wage job” — a job that saved them from foreclosure until her dad found work as a janitor.
Ms. Warren, who also met privately with some tribal leaders while they were in town, offered the group “a promise.”
Each time, she said, “someone brings up my family’s story, I’m going to use it to lift up the story of your families and your communities.”
She vowed to draw attention to health care and environmental inequities on reservations as well as startling statistics, noting that “more than half — half — of native women have experienced sexual violence.”
Ms. Warren was plainly hoping to respond to an article last month in The Boston Globe that raised questions about her commitment to tribal issues.
Yet her remarks made clear that she also sees political opportunity in her long-running feud with Mr. Trump, a way to demonstrate to Democrats that she will aggressively confront him.
“She is taking a perceived liability and not just taking it on, but trying it out as a weapon against the president,” said Mo Elleithee, a longtime Democratic strategist.
Ms. Warren won applause by pointedly invoking one of Mr. Trump’s favorite presidents.
“It is deeply offensive that this president keeps a portrait of Andrew Jackson hanging in the Oval Office, honoring a man who did his best to wipe out native people,” she said.
And when she brought up Pocahontas, she did not just scorn Mr. Trump. She also set aside the fable and talked about the preadolescent Powhatan girl who married a Jamestown settler, helped secure a tenuous peace in colonial Virginia and was ultimately sent to London, where she died at about 21.
“Indigenous people have been telling the story of Pocahontas — the real Pocahontas — for four centuries,” Ms. Warren said, adding, “And, for almost as long, her story has been taken away by powerful people who twisted it to serve their own purposes.”