Sen. Kirsten Gillibrand of New York on Wednesday became the latest Democrat to exit the 2020 presidential primary, announcing that she is scrapping her campaign after failing to meet the fundraising and polling thresholds for September's debate in Houston.

"After more than eight incredible months, I'm ending my presidential campaign," Gillibrand said in a video on Twitter. "We wanted to win this race, but it's important to know when its not your time and to know how you can best serve your commmunity and country."

She added, "I believe I can best serve by helping unite us to beat Donald Trump in 2020."

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The president responded to the news with a jab: "A sad day for the Democrats, Kirsten Gillibrand has dropped out of the Presidential Primary. I’m glad they never found out that she was the one I was really afraid of!"

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Gillibrand is so far the best-known Dem to exit the crowded -- albeit winnowing -- field of White House hopefuls.

In the past two weeks, former Gov. John Hickenlooper of Colorado, Gov. Jay Inslee of Washington state and Rep. Seth Moulton of Massachusetts all dropped out. All three immediately moved on to down-ballot races. Hickenlooper launched a bid for the Democratic Senate nomination in Colorado, while Inslee and Moulton announced re-election bids for their respective offices.

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Gillibrand was elected to her second term in the Senate in 2018 and won't have to face a challenger for her seat until 2024, but she told Fox News last week that she would be open to serving as her party's vice presidential nominee.

“I’m here to serve,” she said. “I can serve in any capacity.”

Gillibrand topped an incumbent Republican in a conservative part of upstate New York to get to the U.S. House in 2007, and was appointed to the Senate two years later, filling the seat vacated by Hillary Clinton, who was tapped to be U.S. secretary of state. Gillibrand later easily retained the seat during a 2010 special election, as well as in 2012 and 2018.

Vocal in the Senate on curbing sexual harassment, and for promoting equal pay for women and family leave, Gillibrand made those issues, coupled with a staunch defense of abortion rights, the spine of her presidential bid. She stood out in the crowded field by becoming the first Democratic presidential hopeful to declare that she'd only appoint judges to the Supreme Court who consider the landmark 1973 Roe v. Wade decision legalizing abortion nationwide a matter of settled law, though most of her competitors quickly followed suit.

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After forming an exploratory committee in January and formally entering the race by calling President Trump a "coward" in a March speech delivered near the New York City tower bearing his name, Gillibrand began with more than $10.5 million left over from her 2018 Senate campaign in her presidential campaign account.

That seemed like more than enough for the long haul.

But Gillibrand was the first Senate Democrat in December 2017 to call for Minnesota Sen. Al Franken's resignation amid allegations of sexual misconduct, and she has said for months that her stance had alienated donors and some voters in his neighboring, make-or-break Iowa.

Many Senate colleagues seeking the Democratic presidential nomination — including Elizabeth Warren of Massachusetts, Cory Booker of New Jersey, Kamala Harris of California and Bernie Sanders of Vermont — followed her lead in calling for Franken to step down before he quit in January 2018. But Gillibrand has continually faced more questions than others about being too quick to condemn him.

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Gillibrand's exit from the primary race could signal that other mid-tier candidates will soon drop out as well, particularly as donors consolidate around the frontrunners, and as the fundraising and polling criteria to make the cut for October’s fourth round of debates remain the same as those for September.

Ten candidates have already qualified to make the stage for the third and fourth debates. They are former Vice President Joe Biden; Booker of New Jersey; South Bend, Ind., Mayor Pete Buttigieg; former Housing and Urban Development Secretary Julian Castro; Harris; Sen. Amy Klobuchar of Minnesota; former Rep. Beto O’Rourke of Texas; Senators Sanders and Warren; and tech entrepreneur Andrew Yang.

Fox News' Paul Steinhauser and The Associated Press contributed to this report.