Warren, once a frontrunner, ends her US presidential campaign

"I may not be in the race for President in 2020, but this fight -- our fight -- is not over," Warren said. "And our place in this fight has not ended."

Warren did not announce any immediate plans to endorse either of the remaining major candidates -- the 77-year-old former vice president Biden, or the 78-year-old leftist senator from Vermont, Sanders.

Biden praised Warren in a tweet following her announcement.

"Senator @EWarren is the fiercest of fighters for middle class families," Biden said. "Her work in Washington, in Massachusetts, and on the campaign trail has made a real difference in people's lives.

"We needed her voice in this race, and we need her continued work in the Senate," he said.

Warren's withdrawal from the race for the top spot on the Democratic ticket against President Donald Trump in November comes after she failed to win a single state on Super Tuesday, including her own.

Her decision comes one day after that of billionaire former New York mayor Michael Bloomberg, who quit on Wednesday after a disappointing Super Tuesday performance of his own and endorsed fellow centrist Biden.

'Going nowhere'

Trump responded to Warren's withdrawal with a tweet mocking her and Bloomberg.

"Elizabeth 'Pocahontas' Warren, who was going nowhere except into Mini Mike's head, just dropped out of the Democrat Primary...THREE DAYS TOO LATE," Trump said.

"She cost Crazy Bernie, at least, Massachusetts, Minnesota and Texas," the president said of three of the states at stake on Super Tuesday. "Probably cost him the nomination! Came in third in Mass."

Warren finished third in her home state of Massachusetts behind Biden and Sanders.

Sanders spoke with Warren on Wednesday but did not say whether he had asked for the endorsement of his fellow progressive.

Warren led some national polls last summer but she never managed to build a broad coalition to carry her through to success in the primaries, finishing behind Sanders and Biden in 14 states on Super Tuesday.

There was no immediate comment from the Sanders campaign on Warren's withdrawal but former South Bend, Indiana, mayor Pete Buttigieg, who dropped out of the race on Sunday, praised her in a tweet.

"Meeting urgency with moral courage, she's the kind of leader Americans are fortunate to have, and I'm honored to have run alongside her," Buttigieg said.

John Kerry, the former Massachusetts senator who lost the 2004 presidential election to Republican George W. Bush, congratulated Warren on running an "inspiring campaign."

'I have a plan for that'

"Massachusetts is lucky to have that kind of leadership on the national stage," Kerry said. "You've inspired millions, including my daughters."

Warren made her mark in the Democratic race on policy strengths but was quickly overshadowed on the left by Sanders, making his second bid for the nomination after losing out to Hillary Clinton in 2016.

One of the most notable moments of Warren's campaign was her debate evisceration of Bloomberg, something she alluded to her in her statement on Thursday.

"In this campaign, we have been willing to fight, and, when necessary, we left plenty of blood and teeth on the floor," she said. "And I can think of one billionaire who has been denied the chance to buy this election."

Kyle Kondik of the University of Virginia's Center for Politics said Warren was squeezed from both sides.

"Warren got crowded out by Sanders to her left and more moderate candidates to her right, to the point where I don't think she had much of a constituency beyond some high-end suburban voters," Kondik said.

The former Harvard law professor cut her teeth on the 2008 financial crisis, guiding president Barack Obama towards creation of a consumer protection agency to help weather the recession.

Her experience as a number-crunching people's advocate helped project her early image as a can-do policy wonk.

"I have a plan for that," she said at rallies, where she pushed proposals for everything from tackling the climate crisis to investing in rural America, rather than focusing like a laser on making 2020 a referendum on Trump.

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