WASHINGTON — Massachusetts Sen. Elizabeth Warren announced Monday that she is establishing an exploratory committee to consider a 2020 White House bid, vowing to be a tenacious advocate for economic fairness and rebuilding the middle class.

In filing paperwork with the Federal Election Commission to allow her to begin raising and spending money to benefit her likely candidacy, Warren becomes the first big-name Democrat to take formal steps to enter what could be a crowded, expensive and extended contest for the party’s presidential nomination.

Warren quickly shared the news with her supporters via email and social media, calling on them to join her in a fight against the "dark path” favored by special interests that she says is hurting the middle class, and political corruption that “is poisoning our democracy."

“Our government is supposed to work for all of us, but instead, it has become a tool for the wealthy and well-connected,” she says in a more than four-minute video announcing her exploratory committee. “If we organize together, if we fight together, if we persist together, we can win."

Warren’s announcement comes days before she is to be sworn in for a second six-year Senate term in the seat once held by John F. Kennedy, the last Democrat to successfully seek the presidency from Massachusetts.

Her 2018 reelection campaign gave Warren more flexibility than other top-tier Democrats to test the themes of a potential 2020 national campaign. After winning more than 60 percent of the vote in November, she vowed in her victory speech to continue her fight “to make our government work not just for the rich and the powerful, but to make it work for everyone.”

Warren also used the campaign to try and address some of her biggest perceived vulnerabilities, most notably in September with the release of results of a DNA test as part of her attempt to address questions about whether her claims of Native American ancestry impacted her professional life as a university professor.

Warren, who grew up in Oklahoma, has said Native American ancestry has been part of her family’s story even as she has acknowledged that it is not formally recognized by the Cherokee Nation. The DNA test performed by a nationally-recognized expert in genetics concluded that there was “strong evidence” that her DNA included Native American ancestry within six-to-10 generations.

The exercise, which included the release of a campaign-style video featuring family members, including a cousin who is a Cherokee Nation citizen, hardly settled the issue. The Cherokee Nation issued a statement calling DNA tests "useless to determine tribal citizenship” and said Warren was undermining their interests. But Warren has sought to move beyond it and said she was simply trying to be transparent.

“This is just who I am,” she told NBC News during a campaign stop in Ohio last month. “I put out 10 years of my tax returns. I’ve put out all my employment records. Yeah, I’ve even taken a DNA test. I’m an open book.”

President Donald Trump has long mocked Warren as “Pocahontas" in direct reference to the controversy. In the video released Monday, Warren focuses primarily on her vision of economic fairness but does not directly mention Trump.

Warren’s academic career, most recently at Harvard, led her to become a leading voice on economic and bankruptcy issues. She helped establish the Consumer Financial Protection Bureau in the Obama administration, but after not being appointed as its first director, she entered the race to challenge then-Republican Sen. Scott Brown.

“I never thought I’d run for office, not in a million years. But when Republican senators tried to sabotage the reforms and run me out of town, I went back to Massachusetts and ran against one of them. And I beat him,” she says in Monday's announcement video.

In winning that high-profile race she became one of the Democratic Party’s strongest grassroots fundraisers and preeminent voices on economic issues. She considered but ruled out running for president in 2016 as Hillary Clinton and Bernie Sanders waged a bitter fight for the Democratic nomination. She endorsed Clinton quickly after the final primary, delivered the keynote address at the Democratic convention and joined her on the campaign trail in the general election.

Her move toward the 2020 race and emphasis on economic fairness puts her into potential direct conflict with Sanders, though she has sought to differentiate herself from the self-described democratic socialist.

“I am a capitalist,” she told CNBC’s John Harwood in July. “I believe in markets. What I don’t believe in is theft.”

Aides say Warren moved quickly to establish an exploratory committee in large part because she, unlike other top Democrats eyeing the race, does not have a leadership PAC. She can transfer the $12 million that remains on hand from her reelection campaign to begin paying political advisers and laying the groundwork for a formal campaign committee, which could be launched within the next two months.