"That is the reason why I'm in the fight", she told reporters.
Warren also denounced potential billionaire candidates who plan on self-funding their campaigns.
The 54-year-old, who hit the headlines for her tough questioning of Mr Trump's supreme court pick Brett Kavanaugh and former attorney-general Jeff Sessions, has also been visiting states that hold early nominating contests.
Here is what you need to know about Warren's trip. And on that front, there were mixed views on Warren's approach so far.
Even when Sioux City Democrat Tricia Currans-Sheehan asked her why she submitted to a DNA test after Trump questioned Warren's claim of Native American ancestry, Warren shifted back to economic fairness. Elizabeth Warren is introducing herself to influential Iowa Democrats by telling her personal story of economic opportunity, trying to lay claim in the emerging 2020 presidential field as a champion for a middle class she says is withering under President Donald Trump.
"This is just the beginning, I'm excited to see it start", said Lisa Koch, 48, an attorney from Council Bluffs who said she was a long-time fan of Warren's but anxious her gender, age or combative approach might turn off some voters.
"I'm not a person of color", Warren told the audience. I'm not a citizen of a tribe. "And I respect that difference". "But I have had a chance to talk about Medicaid, partly because I think we've had a national conversation about health care, and I think it's been enormously valuable".
She is a self-described defender of the ordinary American against powerful interests and was one of Mr Trump's fiercest critics during the 2016 presidential race. "But what I can do is I can be in this fight for all of our families".
A better-than-expected finish in Iowa could position Warren well in New Hampshire, where she would be expected to perform well as a neighbor to the first-in-the-nation primary state.
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"No one's raised it", she said. "Hillary [Clinton], in the debates, kind of let him run over her. Trump would make a big mistake to go after her". "And so I'm not sure she should have gotten into it, but anyway I hope she learned from it". "Today, a minimum wage job in America will not keep a momma and a baby out of poverty. And that is wrong".
But what will it take to win the party's primary - and then the presidency? Instead, months later, Warren is still answering questions about her perceived connection to tribal ancestry. He's most concerned about the cost of his prescription medication, which he has to pay almost $300 for out of pocket.
But her decision in 2020, Wertz said, would turn on more concrete questions. "She's being portrayed in the right wing media as this wild-eyed liberal from the East Coast", said Bill Shackelford, a retiree from Des Moines.
The announcement that Warren, a liberal from MA, will shut down the Elizabeth Warren Action Fund, came from her spokeswoman, Kristen Orthman.
Outside Warren's debut event on Friday night, Natalie Wertz, 29, who was waiting for the candidate with a friend - both of them having purchased pink T-shirts emblazoned with Warren's de facto slogan, "Nevertheless, she persisted" - spoke confidently of Warren's potential as a candidate.
"All three of my brothers still live in Oklahoma".
Her call for billionaires not to self-fund campaign operations follows CNBC's reporting that Democratic donor and former New York City Mayor Mike Bloomberg was prepared to spend more than $100 million on his own campaign organization if he were to run in 2020. "I'm going to stay focused on that all the way through".
She then shifted back to her core message: "What I can do is I can be in this fight for all of our families".