Her announcement came 13 months before the Iowa caucuses that launch what is expected to be a boisterous primary season.

“America’s middle class is under attack,” said a video message from Warren, who has represented Massachusetts in the Senate since 2013, crafting a reputation as an economic populist.

“Corruption is poisoning our democracy,” she said.

“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.”

That, she said, is why she is launching her exploratory committee.

A former public-school teacher and then Harvard law professor, Warren has been a vocal advocate of consumer and workers’ rights. But Americans may know her best for her frequent sparring with Trump – which has had mixed results.

Warren has denounced Trump as an “insecure money grubber” with a platform of “racism, sexism and xenophobia”, while Trump has described her as “goofy” and a “low-life” with “a nasty mouth”.

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Warren’s searing criticisms of Trump’s trade policies, erosion of consumer protections, and openness to authoritarian regimes – not to mention her call in September for Congress to use a constitutional manoeuvre to remove him from office – have drawn his attention, and his disdain.

Reacting to her latest move, Trump said he was unsure whether Warren could replace him at the White House.

“You’d have to ask her psychiatrist,” he quipped in an interview with Fox News.

“We’ll see how she does. I wish her well, I hope she does well, I’d love to run against her.”

At his election-style rallies, Trump took to mocking her claim to have some Native American heritage by dubbing her “Pocahontas”, a derisive reference to the 17th century Native American who lived in what is now Virginia.

Long mocked by Trump as ‘Pocahontas’, US Senator Elizabeth Warren releases DNA evidence of Native American ancestry

When Trump offered to donate US$1 million to Warren’s favourite charity if she took a test proving “you’re an Indian”, she eventually did so, hoping to put an end to his ridicule.

Instead, he seemed to relish the fact that the test showed her with only a sliver of Native American heritage.

With as many as three dozen Democrats weighing possible presidential bids, the road to the nomination will be arduous.

Among those who have already declared their intention to run are Julian Castro, a former housing secretary in Barack Obama’s administration, Maryland Representative John Delaney and Richard Ojeda, a former army paratrooper currently serving as a state senator in West Virginia.

Polls for now show Warren trailing veteran politicians like former vice-president Joe Biden and Senator Bernie Sanders, both in their 70s – as well as rising young star Beto O’Rourke, who is 46.

But analyst Nate Silver said on Twitter that Warren “probably has a better chance than Sanders of bridging the gap between the left and the party establishment”.

“She’s always raised a tonne of money. Voters know what she stands for. Women did well in the 2018 primaries,” Silver added.

Warren has built the framework of a serious campaign, with a staff of more than 70 people, US$12.5 million left over from her successful re-election effort, and a nationwide network of contacts and supporters.

As she seeks to raise her profile, Warren likes to tell how she grew up in the Central Plains state of Oklahoma, in a family she said lived “on the ragged edge of the middle class”.

After her father suffered a heart attack, she went to work at age 13 waiting tables in a restaurant – life experience she says gives her a visceral connection to ordinary Americans.

Agence France-Presse, Reuters