Warren is among the first Democrats to take a formal step for the party's nomination to take on President Donald Trump in 2020. The field is expected to grow in the coming weeks as other Democrats enter what will likely become a crowded and expensive primary contest.
Warren is already planning to travel to the early caucus and primary states, including Iowa, in the coming weeks, according to a source with direct knowledge of the matter.
Iowa Democratic Party Chair Troy Price received a phone call from Warren herself on Monday and the two discussed a visit to the Hawkeye state, according to a person familiar with the conversation. Warren did not commit to a specific date but did say she was planning on making the trip "soon." A political operative within the state who spoke on the condition of anonymity said Warren could make it out to the key caucus state as early as next week.
Further, Warren's advisors had already begun reaching out to potential staffers in the primary state of South Carolina, including as recently as last week, a party operative from the Palmetto State told CNBC on the condition of anonymity.
A person close to the Massachusetts Senator says she's looking to get a head start to "build an apparatus, identify and hire staff, build out operations, and plan for early states."
Prior to her announcement, Warren reportedly deployed members of her team to the early primary states and other key electoral states such as Ohio, Florida, Wisconsin and Michigan to meet with possible field organizers. Now that she's announced her exploratory committee, Warren can go to these same states to personally meet those who may work for her.
Some progressive groups rallied around the news. In a statement, the Progressive Change Campaign Committee, which ran the original "Draft Elizabeth Warren for Senate" campaign in 2011, called Warren "the most electable among many potential contenders with progressive positions."
"If she runs, she will be best equipped to defeat Trump because voters want someone instinctively on the side of working people and willing to challenge power -- from Wall Street banks, Big Pharma, and big polluters to systemic racism and gender inequity," said the group's co-founders, Stephanie Taylor and Adam Green.
In an early poll of the 2020 race conducted by the progressive organization MoveOn.org, Warren was among the top contenders with 6.4 percent of the vote.
She trailed Sen. Kamala Harris, D-Calif., and Sen. Bernie Sanders, I-Vt., as well as former Vice President Joe Biden and Rep. Beto O'Rourke, D-Texas, who received the most votes at 15.6 percent. The group endorsed Sanders in 2016.
The Massachusetts Democrat, a prominent voice in the party's liberal wing, has vowed to go after major banks and protect consumers from predatory practices. She is credited with drafting, as an academic, the original plans for a Consumer Financial Protection Bureau.
Warren, whose announcement was widely expected, has come under fire in recent months for her decision to release a DNA test earlier this year that showed small amounts of Native American heritage in her ancestry.
The move was criticized by Native American groups and mocked by Trump, who derisively refers to the senator as "Pocahontas" at rallies and on social media.
In November, she was re-elected to her U.S. Senate seat with 60 percent of the vote.
Several of Warren's senate colleagues are thought to be weighing presidential bids of their own, including Harris and Sanders, as well as Sen. Cory Booker of New Jersey, Sen. Sherrod Brown of Ohio and Sen. Amy Klobuchar of Minnesota.
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