WASHINGTON - U.S. Senator Elizabeth Warren, a liberal firebrand and Wall Street antagonist, took the first step toward a 2020 White House run on Monday, becoming the most prominent Democrat to announce a challenge to Republican President Donald Trump.

Warren said she had formed an exploratory committee, which will allow her to begin raising campaign funding as part of what is expected to be a crowded Democratic field before the November 2020 presidential election.

Warren, 69, who became a senator from Massachusetts in 2013, has frequently clashed with Trump, who has cast aspersions on Warren’s claim to Native American ancestry and mockingly referred to her as “Pocahontas.”

Warren released a video in which she outlines her vision of a path to opportunity for all Americans, not just the wealthy.

“Every person in America should be able to work hard, play by the same set of rules, & take care of themselves & the people they love,” she said in a Twitter post. “That’s what I’m fighting for, & that’s why I’m launching an exploratory committee for president. I need you with me.”

Warren said in September she would take a “hard look” at running for the Democratic nomination to challenge Republican Trump in 2020. The former Harvard Law School professor campaigned with Democratic presidential candidate Hillary Clinton in 2016 and attacked Trump as an “insecure money grubber” driven by greed and hate.

Earlier this month, Julian Castro, 44, who was mayor of San Antonio and secretary of the Department of Housing and Urban Development under Democratic President Barack Obama, said he was forming an exploratory committee and would announce his intentions on Jan. 12.

In 2017, former Democratic congressman John Delaney of Maryland said he would seek the party’s nomination.