Sen. Elizabeth Warren took a major step Monday toward an all-but-certain 2020 White House run, seeking to become the Democratic nominee to challenge President Trump on a message of economic equality and fighting corruption.

The Massachusetts progressive said in a New Year’s Eve email and video message to supporters that she’s launching an exploratory committee for a presidential run, which would give her a potential early edge in fundraising and organization. She said American families were “under attack from every direction,” because of a government that’s “bought and paid for by a bunch of billionaires and giant corporations that think they get to dictate the rules.”

Warren previewed her populist message in a recent interview with Bloomberg News.

“I’m in this fight for hard-working families. And that means reducing the student loan debt burden, increasing our Social Security payments for those who depend most on it, and the overarching piece, reducing corruption in government,” the senator said.

“Right now, Washington works great for the wealthy and the well-connected, it’s just not working for much of anyone else,” Warren said.

Warren, who handily won a second six-year Senate term in November, said she wants to defend the Affordable Care Act from Republican attacks and “find a system of Medicare available to all that will increase the quality of care while it decreases the cost of all of us.”

Warren has become a polarizing figure because of her aggressive criticisms of Wall Street, her support for raising taxes on rich Americans to mitigate income inequality, and her push to regulate large corporations that she often depicts as preying on ordinary people.

But that same advocacy, which dates back to her time as a Harvard law professor, has endeared her to a progressive base full of voters who are hungry for a sharp left turn by the Democratic Party.

“She was doing populist economics before everybody thought it was cool. So she has a background and message that has met its moment,” said Mary Anne Marsh, a Democratic consultant based in Boston, who argued that Warren is a front-runner because “she’s spent the better part of the last 18 months laying the groundwork for this moment.”

Warren already has the building blocks of a campaign apparatus, including a dedicated staff and a policy platform.

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