Elizabeth Warren ends her presidential campaign

Warren said she was not going to make an announcement about endorsing another candidate for president on Thursday.

"I need some space around this," Warren said, "and I want to take a little time to think a little more."

Warren's path to the nomination has been narrowing since the first round of voting in Iowa, where she placed third. In subsequent contests in New Hampshire and Nevada, she dropped down to fourth. In South Carolina, she came in a distant fifth.

The New York Times first reported that Warren is exiting the race.

Despite the mounting setbacks, Warren's campaign was as recently as Sunday touting a plan to amass delegates through the late spring and make a play for the nomination, as a unity candidate, during the Democratic National Convention this summer. But those hopes were effectively dashed on Super Tuesday, when she failed to win her home state of Massachusetts, finishing third behind former vice president Joe Biden and Sen. Bernie Sanders, and mostly underperformed in a series of key states.

Her exit officially leaves Biden and Sanders as the final top contenders for the Democratic nomination.

Her departure follows those of Minnesota Sen. Amy Klobuchar and former South Bend, Indiana, Mayor Pete Buttigieg, the latter of whom finished ahead of Warren in each of the four early state contests. Their rush to Biden, and the moderate consolidation that followed, combined with Sanders' lock on progressive voters left Warren in a political no-man's land. Former New York Mayor Michael Bloomberg exited the race on Wednesday.

Both Klobuchar and Buttigieg endorsed Biden on Monday. Warren, a respected progressive leader who has been fiercely critical of the former vice president and, at least until the current campaign heated up, a friend and ally of Sanders, has not yet indicated who she will support moving forward. Sanders said he spoke to Warren on Wednesday, but did not share any details from their conversation.

Once considered a leading contender for the nomination, Warren's plummet began months before the first ballots were cast in what was a crowded primary field that saw multiple candidates shoot up in the polls before being batted down by their rivals. Of those who dropped out of the race before her, she was endorsed only by former Housing and Urban Development Secretary Julián Castro. He threw his support to Warren in early January, about a month before Iowa, but despite his passionate advocacy, failed to arrest her slide.

Warren was, at first, tripped up by the controversy surrounding her decision to publicize a DNA test meant to prove her Native American ancestry. She apologized to Native American leaders for both the DNA test and her controversial past claims.

She swore off big donors and began a trail tradition that became one her trademarks: a "selfie" line that followed her events and allowed voters to share a brief but intimate moment with the candidate

Warren touted her grassroots fundraising efforts by posting clips online of her calls to small dollar contributors and began doing a "pinkie promise" with some of her youngest female supporters, "so that they'll remember that running for president is what girls do."

Her campaign really took off in the spring and summer 2019 as she rolled out a comprehensive suite of what would eventually add up to more than 70 policy plans, addressing everything from anti-corruption legislation to the Green New Deal.

By the fall, she was leading in a number of early state polls and appeared to have gained a foothold with liberal voters around the country. They embraced her as the candidate with "a plan for that" -- an identity the campaign embraced and ran with -- and, in some progressive circles, was viewed as the more electable option over fellow favorite Sanders.

But her standing began to slip in the fall, when her support for "Medicare for All," the universal, government-run medical insurance program, came under stricter scrutiny from moderate rivals like Biden, Klobuchar and Buttigieg. In response, she released a pair of proposals: one to finance Medicare for All without raising any taxes on middle class voters and another that would have effectively broken up the bill into two pieces.

Warren's attempts to quiet the critics backfired. Opponents of Medicare for All, boosted by an industry spending campaign designed to drive down its popularity, continued their attacks. Progressives, too, became dissatisfied, voicing concerns over the senator's commitment to passing the legislation.

By the Iowa caucuses, Warren had fallen behind Sanders and had begun to see a sizable number of her more moderate supporters flock to Buttigieg, who, despite their political differences, also appealed to more affluent, white college-educated voters.

But the crushing blow likely came later, in South Carolina, where she finished a distant fifth.

Throughout the campaign, Warren kept up a concerted effort to directly address the African-American community. Her targeted plans-within-plans sought to combat economic and social inequality with proposals that acknowledged and offered policy solutions that she argued would begin to undo generations of systemic discrimination in everything from housing to health and business. But when the contest arrived in down South, her attempts to make inroads into the community fell flat.

Despite those setbacks, the campaign continued to argue that Warren was the only candidate who could bridge the Democratic Party's divisions -- a progressive with the credentials and charisma to win over voters across the ideological spectrum.

By February, though, the campaign -- which had spent its dollars in anticipation of a long nomination fight -- was in a cash crunch. She got a fundraising boost after a lauded debate performance in Las Vegas, where she targeted Bloomberg over the billionaire's past treatment of women at his company and his support for "stop and frisk" during his time as mayor of New York City.

But because of high early voting in Nevada, which happened before the debate, the bump that followed didn't translate into a surge of support in the state's caucuses days later.

In the final weeks of her campaign, Warren also relented on her long-standing refusal to accept the support of a super PAC, which ended up spending heavily -- in excess of $13 million during its brief run -- across the Super Tuesday map, arguing that she would not unilaterally disarm in an increasing expensive campaign.

As her prospects dwindled, Warren increasingly turned her fire on Sanders, arguing that, for all their policy agreements, he was -- unlike her -- an ineffectual legislator with a short resume of accomplishments during three decades in Congress. The turn began to upset some progressives who worried that her criticism would damage the Vermont senator at a time when moderates were coalescing around Biden.

But there is no clear sign that Warren's departure, without a vocal endorsement and energetic campaigning on his behalf, will benefit Sanders. Her coalition of support was ultimately too thin to vault her into the upper tier of the primary, but its ideological diversity likely means that it will splinter among the remaining candidates.