U.S. Sen. Elizabeth Warren ended her presidential bid on Thursday, declining to immediately endorse any of the remaining Democratic contenders and hinting she'll talk more in the future about gender issues in a campaign that at one time included six women candidates.

Addressing reporters outside her Cambridge home, Warren called running for president "the honor of a lifetime" and said she had no regrets.

"I say this with a deep sense of gratitude for every single person who got in this fight, every single person who tried out a new idea, every single person who just moved a little in their notion of what a president of the United States should look like," she said. "I will not be running for president in 2020, but I guarantee I will stay in the fight for the hard-working folks in this country who have gotten the short end of the stick over and over."

Warren's withdrawal comes more than a year after she jumped into the race during a rally in Lawrence, and two days after coming in third in her home state's Democratic primary.

The senior senator from Massachusetts did not endorse any of the three Democrats remaining in the race, which has been dominated recently by Vermont Sen. Bernie Sanders and former Vice President Joe Biden. U.S. Rep. Tulsi Gabbard of Hawaii is also still running.

Asked what she'd tell her supporters about who to get behind now, Warren said, "Let's take a deep breath and spend a little time on that. We don't have to decide this minute."

One of the hardest parts of her decision, she said, was "all those little girls who are going to have to wait four more years" to potentially see a woman in the White House. Warren said she would have "a lot more to say" later about the issues of sexism and gender in the race.

Warren said discussing gender in the 2020 presidential race is a "trap question for everyone."

"If you say, 'Yeah, there was sexism in the race, everyone says, 'Whiner!'" she said, adding that if you say sexism was not a factor, "About a bazillion women think, 'What planet do you live on?'"

Warren said she was told when she first entered the race that there were "two lanes" -- a progressive lane led by Sanders and a moderate lane led by Biden -- and "no room for anyone else in this."

"I thought that wasn't right, but evidently I was wrong," she said.

Echoing comments she made after casting her ballot on Tuesday, Warren said she was glad for the opportunity to elevate issues like universal child care, her proposal for a wealth tax, higher Social Security payments and cancellation of student loan debt.

Another one-time candidate, former Gov. Deval Patrick, said on Twitter that Warren "and her team drove an energized, disciplined, and important campaign committed to big ideas, grassroots organizing, and fighting for what you believe in."

"We need her leadership to win - - and to deliver real change when we do," Patrick said.

Warren on Thursday became the third Massachusetts Democrat to drop out, after Patrick and U.S. Rep. Seth Moulton. Former Gov. William Weld is in the midst of a longshot primary challenge against President Trump.

"There's no question that she put everything she had into it," Gov. Charlie Baker said after an event in Quincy, according to a recording provided by his office.

Congressman Joe Kennedy III, who backed Warren from the start of her campaign, tweeted about the importance of her candidacy to his young daughter.

"To my Senator, my professor, and most importantly my friend @ewarren — you made this race better, our country better. Most importantly you let millions of little girls, just like Ellie, know that running for President is what girls do," Kennedy wrote.

President Donald Trump, who is likely looking at Biden or Sanders as a general election opponent, suggested that Sanders might have done better in Tuesday's voting if Warren had stepped out of the race earlier.

"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 tweeted. "She cost Crazy Bernie, at least, Massachusetts, Minnesota and Texas. Probably cost him the nomination! Came in third in Mass."

Kennedy didn't say who he will support, and Sen. Edward Markey, in the midst of a primary challenge from Kennedy, said he'll "be taking some time to consider who I will support."

"My head and heart are with Elizabeth Warren. Her inspirational campaign made the country smarter and more engaged," Markey said. "I was so proud to vote for her and am honored to be her partner in the U.S. Senate. Donald Trump is the worst president in American history. I am committed to defeating Donald Trump on Election Day, and I will support the party's ultimate nominee."

Massachusetts Democratic Party Chairman Gus Bickford called Warren a "fierce fighter with a passion for justice and for leveling the playing field."

"Her candidacy elevated the conversation and provided countless contributions to the race for President," Bickford said. "I thank her, and her team, for their tireless efforts and inspiring campaign. The work Senator Warren's campaign has done over the last 14 months will help ensure that this country elects a Democrat in November."

Barbara Lee, president and founder of the Barbara Lee Family Foundation, noted that Warren is the fourth sitting Democratic woman senator end her campaign - she follows Sens. Amy Klobuchar, Kamala Harris and Kirsten Gillibrand - and said Warren "set the standard, challenging her rivals to be more thoughtful and more specific."

"She has been tireless and full of boundless energy — during her endless selfie lines, packed campaign rallies, and during her strong debate performances," Lee said. "She hit back against sexist criticism, and she outlasted 24 rivals."

Baker praised Warren for taking on a presidential campaign, and the endurance such a race demands.

"I don't think anybody would question the heart and soul she put into it," said Baker, who has run three statewide campaigns and could seek a third term. "I mean every time I saw her she was either running from an event or running to an event. And I'm sure this is a major disappointment for her and many of her supporters." The governor called running for public office a "high anxiety sport."

Republican Beth Lindstrom, a 2018 U.S. Senate candidate who worked in state government for former Gov. Mitt Romney and led Ambassador Scott Brown's first U.S. Senate campaign, suggested Warren's presidential run should be fodder for voters should Warren seek a six-year Senate term in 2024.

"While @ewarren was running for President- she’s left us without a true advocate in the Senate that could work with others," Lindstrom tweeted. "Next time, pick someone who will take care of your concerns and not someone who wants to ditch you for fame, Massachusetts!"