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(CNN) —  

Massachusetts Sen. Elizabeth Warren took a major step toward a presidential run on Monday, announcing in a video message and email to supporters that she is forming an exploratory committee ahead of an expected campaign for the Democratic nomination in 2020.

With her announcement 13 months before the Iowa caucuses, Warren, who became a progressive star by taking on Wall Street after the 2007 financial crisis and, more recently, President Donald Trump, is the first Democrat with a national profile to take formal action ahead of an anticipated presidential campaign.

In a four-and-a-half minute video, Warren made clear she would not shy away from the pugilistic tone and themes that catapulted her to national prominence in her upcoming presidential run: economic equality, government accountability and the reining in of big corporations.

“Corruption is poisoning our democracy,” Warren says in the video as images of Republican leaders flash across the screen. “Politicians look the other way while big insurance companies deny patients life-saving coverage, while big banks rip off consumers and while big oil companies destroy this planet.”

The clip begins with the senator recalling a hardscrabble childhood in Oklahoma – her mother got a minimum-wage job after her father suffered a heart attack. He would eventually work as a janitor.

“He raised a daughter who got to be a public school teacher, a law professor and a senator. We got a real opportunity to build something,” Warren says. “Working families today face a lot tougher path than my family did.”

In one of multiple nods in the video to racial inequality, she adds that “families of color face a path that is steeper and rockier, a path made even harder by the impact of generations of discrimination” – an early acknowledgment of the political importance of appealing to and winning the support of minority voters.

As she warns of a deepening crisis faced by the American middle class, Warren points a finger squarely at the Republican Party, using images of former presidents Ronald Reagan and George W. Bush, along with grinning cameos from Treasury Secretary Steven Mnuchin, departing House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell and Trump.

Warren is a searing critic of the President, and Trump has responded by openly mocking her Native American heritage and referring to her as “Pocahontas.” Her decision in October to respond to Trump and other critics by releasing the results of a DNA test aimed at proving her ancestry fell flat with many Democrats and overshadowed her midterm message.

In an interview with Fox News on Monday, Trump skewered Warren over the test and said he would “love to run against her.”

Asked whether he thought Warren believed she could defeat him in 2020, Trump said, “I don’t know. You would have to ask her psychiatrist.”

Warren’s announcement also comes in the midst of a prolonged partial government shutdown over Trump’s insistence on funding for a border wall, which has caused political chaos that has spooked investors and sparked turmoil in the stock market. This backdrop could prove to be a boon for Warren, who is widely expected to build a campaign centered around her signature economic populist message and anti-corruption platform.

By launching an exploratory committee, Warren can begin raising money for the coming campaign. Despite swearing off corporate PAC money, she enters the 2020 cycle with $12.5 million left over from her 2018 Senate campaign, according to Federal Election Commission records. Warren can transfer that money into her presidential coffers.

Speaking to reporters on Monday, Warren suggested she was unlikely to seek the assistance of a big-money outside group.

“I don’t think we ought to be running campaigns that are funded by billionaires, whether it goes through super PACS or their own money that they’re spending,” she said. “Democrats are the party of the people, and the way we make that clear is we join together and we fund our campaigns, we make our campaigns work through the people.”

Warren added, “I’ve already received donations from all 50 states, the District of Columbia and Puerto Rico. That’s how you build a grassroots campaign, that’s what I believe.”

A source close to Warren has said the timing of Monday’s announcement – on New Year’s Eve, when most people aren’t plugged into the news – had more to do with a need to “build an apparatus” by “identifying and hiring staff” than influencing other contenders’ plans.

But some Democratic operatives are skeptical, and one fundraiser suggested the Warren team might be hoping that a hefty day-one haul, made public in early 2019, could cause potential rivals to reconsider their options.

“It’s a gamble that folks will give a ton of small money today,” the Democrat said.

Rufus Gifford, former President Barack Obama’s 2012 campaign finance director, made the same point in a tweet.

“Elizabeth Warren must think she can put up huge $$ numbers on her January report - scaring others out of the race,” he wrote. “Only reason I can figure you’d launch a Presidential Campaign on New Year’s Eve.”

Even before Monday’s notifications went out, the work of building the infrastructure to support a presidential bid had been well underway.

Since her re-election to the Senate in November, Warren has made hundreds of calls to political grassroots leaders in the early states of Iowa, New Hampshire, South Carolina and Nevada, the source said. She is expected to hit the campaign trail later this week if no votes are scheduled to end the government shutdown.

Warren’s staff members are also having discussions with operatives in those states and are in the process of searching for campaign office space in the Boston area, the expected location of her presidential campaign headquarters.

Dan Geldon, Warren’s longtime aide who served as her chief of staff in the Senate and was once the senator’s student at Harvard Law School, is likely to serve a senior role in the eventual Warren campaign, the source said.

More than a year out from the first round of voting and with months to go until the first debate, the coming Democratic primary is already shaping up to be one of the most fierce and feisty nominating contests in a generation.

Warren’s work to establish and defend the Consumer Financial Protection Bureau, or CFPB, made her a star among progressives who first pushed for what would be a successful 2012 Senate run and then, with less luck, a presidential bid she ultimately passed up four years later.

This time around, the large Democratic field is expected to include multiple candidates touting progressive platforms – a reality that underscores her influence within the party but could also complicate her path to its nomination.

Some two dozen candidates are said to have shown interest in a 2020 bid. Warren’s national profile, which traces back to her work as a watchdog following the 2008 bank bailouts, immediately places her among the favorites, alongside former Vice President Joe Biden, Vermont Sen. Bernie Sanders and rising star Beto O’Rourke, the departing Texas congressman who just lost a bid for the US Senate.

A CNN/Des Moines Register/Mediacom survey earlier this month of likely Iowa caucusgoers found Warren with 8% support, trailing Biden (32%), Sanders (19%) and O’Rourke (11%) – numbers broadly consistent with other early national polling.

Warren welcomed the coming fight during her remarks on Monday, and in particular, the potential for a crowded field of progressive hopefuls.

“I think it’s great that we have a strong and growing group of Democrats who are making these arguments, who are fighting these fights,” she said. “That’s how we build a movement – we do it together.”

Warren’s decision to more formally begin the process comes less than a month after the editorial board for her hometown newspaper, the Boston Globe, ruffled progressive feathers by suggesting she consider abandoning a potential run.

“Warren missed her moment in 2016, and there’s reason to be skeptical of her prospective candidacy in 2020,” the board wrote in early December, citing a poll from September 2018 that put former Massachusetts Gov. Deval Patrick, a Democrat who has since ruled out a presidential run this cycle, ahead of Warren.

It also suggested she had become too much of a “divisive figure,” an apparent reference to the heavily publicized DNA test. It confirmed Warren had distant Native American ancestry, but was met with backlash from some tribal leaders, activists and outspoken Democrats who fretted over whether Warren had played into Trump’s hands.

In a statement Monday, Republican National Committee Chair Ronna McDaniel gave a preview of the attacks to come, dismissing Warren as “another extreme far-left obstructionist and a total fraud.” McDaniel also took a swipe at what she described as Warren’s “phony claim to minority status.”

Cherokee Nation Secretary of State Chuck Hoskin Jr. was among the most outspoken critics and said in October that Warren had undermined “tribal interests.”

“Using a DNA test to lay claim to any connection to the Cherokee Nation or any tribal nation, even vaguely, is inappropriate and wrong,” Hoskin said in a statement.

But any early missteps – or even disappointing polling – are unlikely to dampen excitement among the party’s increasingly influential progressive bloc.

“Elizabeth Warren, on a visceral level, is fighting for everyday people and against powerful interests,” Progressive Change Campaign Committee co-founder Adam Green said, “and that comes through with an authenticity this moment demands.”

Green, whose group has supported Warren for years while talking up “the Warren wing” of the Democratic party, also gave a hint of how his group and potentially others might seek to distinguish the Massachusetts senator from other leading contenders.

“There are different theories on being effective, but she believes in picking issues that are super popular and forging coalitions to win on those issues,” he said. “Others can be more of a loner, or willing to charge into battle first before having a fully baked plan.”

CNN’s Fredreka Schouten and Dan Merica contributed to this report.