BOSTON – Elizabeth Warren, a Massachusetts senator whose brand of big tech-busting, corruption-fighting liberal politics at one time made her a front-runner in the race for president, ended her campaign.

Warren said outside her Cambridge, Massachusetts, home that she would not endorse a candidate yet.

"Not today," she said when asked about an endorsement. "I need some space around this and a little time to think a little more."

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Warren's departure from the Democratic primary comes after a disastrous Super Tuesday when she didn't finish above third in any state, building her streak to 19 contests that she lost. She even lost her home state, finishing a distant third in Massachusetts.

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Warren campaigned on a mantra of "big structural change" to tackle political corruption and money in politics, while championing a slew of liberal causes such as "Medicare for All," retiring student debt and breaking up big tech such as Facebook.

The 70-year-old second-term senator, who led in national polls in November, faced a serious setback in the rocky rollout of a plan to pay for her $20.5 trillion health care overhaul. It undercut one of her strengths – that she's in command, well-prepared and an expert on policy. "I've got a plan for that," she often said in speeches.

She never rebounded, finishing third in the Iowa caucuses before a dismal fourth-place showing in New Hampshire, followed by similar results in Nevada and South Carolina.

Joe Biden is the primary race's new front-runner ahead of Sen. Bernie Sanders after the former vice president dominated Super Tuesday, when he coalesced support among the party's establishment, moderates and African American voters.

An official with Biden's campaign confirmed that Biden spoke with Warren by phone yesterday. The official would not comment on Warren's political plans, including an endorsement.

Sanders said he spoke to Warren on Wednesday, saying, "We spoke on the phone a few hours ago, and what Sen. Warren told me is she's assessing her campaign. She has not made any decisions at this point.”

A Morning Consult poll found Sanders and Biden would benefit roughly equally from Warren's departure. The poll says 43% of Warren's supporters choose Sanders as their second choice, compared with 36% who say Biden is their second option. The margin of error in the poll taken Monday and Tuesday is plus or minus 4 percentage points.

A Democratic friend of Sanders who has worked with him said people shouldn't assume he will win the endorsement of Warren. There is a definite party shift to Biden, he said, and Warren has her own future to think about: "If she wants to stay viable, she'll endorse Biden."

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Warren, a former Harvard law professor who led the Consumer Financial Protection Bureau under President Barack Obama, was squeezed from competing sides within the Democratic electorate.

Her advantage among college-educated Democrats eroded when some of them chose the bipartisan, unity-driven message of Sen. Amy Klobuchar and Pete Buttigieg over Warren's pitch to lead the "fight" to bring about change.

Warren lost the party's far left, in particular people 18 to 29 years old, overwhelmingly to Sanders. These were the voters most likely to gravitate toward Warren's economic populist message, but in Sanders, they picked a democratic socialist pitching much the same. Throughout the campaign, Warren struggled to attract support from African Americans and other minority voters.

It left Warren without a reliable base among a sea of contenders. The campaign-spending onslaught of billionaire Mike Bloomberg pushed Warren further out of the picture.

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Bloomberg, Buttigieg and Klobuchar endorsed Biden after exiting the race.

Warren told reporters that before she entered the Democratic primary she was told two lanes existed – the progressive lane held by Sanders and a moderate lane occupied by Biden – and there was no room for anyone else.

“I thought that wasn’t right, but evidently I was wrong.”

Asked whether sexism played a role in her failed bid, Warren said that’s a “trap question” for any woman to answer.

“If you say, 'Yeah, there was sexism in this race,' everyone says, 'Whiner.' And if you say, 'No, there was no sexism,' about a bazillion women think, 'What planet do you live on?' I promise you this: I'll have a lot more to say on that subject later on."

Warren's first election came in 2012 when she challenged and unseated Sen. Scott Brown, R-Mass., who held the former Senate seat of Ted Kennedy after his death three years earlier.

Warren entered the race against Brown down double-digits in polling but ended up winning 54%-46% in the Democratic-leaning state. She was reelected to a second term in 2016, easily defeating Geoff Diehl, a Republican state representative.

Warren was encouraged by many liberal activists to run for president in 2016, but she passed, opening a lane for Sanders to launch a campaign to the left of Hillary Clinton. Although he lost, the support Sanders coalesced among the party's left carried over into his current run at the expense of Warren.

Warren's entry into the 2020 election was prefaced by her highly criticized decision in October 2018 to release DNA results that showed "strong evidence" she had Native American heritage dating back six to 10 generations.

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It was an attempt to get ahead of attacks she faced in the presidential race for claiming Native American heritage. Republicans and President Donald Trump relentlessly mocked Warren as "Pocahontas." Trump promised a $1 million donation to a charity of Warren's choice if DNA results proved her claims.

Her release of the DNA results set off a backlash from Native American groups, including the Cherokee Nation, which slammed her decision to use DNA testing to claim Native American heritage as "inappropriate and wrong." The group said Warren is "undermining tribal interests with her continued claims of tribal heritage.” Warren apologized.

The issue over Warren's ancestry goes back to the 1980s, when as a law professor at the University of Texas-Austin, she listed herself as a minority professor in the Association of American Law Schools. There's no known evidence that she listed herself as Native American when she was hired by the University of Pennsylvania and later Harvard.

Known to jog on stage to address her supporters, the energetic Warren began her speeches by discussing her humble upbringing in Oklahoma, marriage to her high school sweetheart and her quick divorce that left her a single mother in Texas. She graduated from the University of Houston and remarried to Bruce Mann, who was hired at Harvard as a law professor several years after Warren.

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Warren cast herself as a lifelong "fighter," from her time growing up to her challenge of Brown, as she argued that she was the Democrat best equipped to take the "fight" to Trump.

She reminded voters of the tagline "Nevertheless she persisted," a comment by Senate Majority Leader Mitch McConnell, R-Ky., referring to Warren's objection to Trump's appointment of Jeff Sessions as attorney general. It became a rallying cry for many Democrats.

As she stumbled out of the gate, Warren tweaked her pitch by calling herself the candidate who could unite the fragmented Democratic coalition in the general election. Sanders has faced questions about his ability to unify all factions of the party against Trump.

Although Warren's bid for president fell short, she is still among the leading liberals in the Senate, where she has four years left in her second term.

Reach Joey Garrison on Twitter @JoeyGarrison.