Out of the running: On the qualifying deadline for the September debate stage, Gillibrand dropped out of the race. "We have to defeat President Trump, flip the Senate, and elect women up and down the ballot," she said in a video posted to Twitter. She is the first female candidate to drop out.
Name: Kirsten Elizabeth Gillibrand
Date of birth: Dec. 9, 1966
Hometown: Albany, New York
Family: Husband to Jonathan Gillibrand, mother to two sons
Education: J.D., UCLA School of Law (1991); A.B., Dartmouth College (1988, magna cum laude)
What she does now: U.S. senator for New York since 2009
What she used to do: She served in New York’s 20th Congressional District from 2007 to 2009; served as special counsel to Secretary of Housing and Urban Development Andrew Cuomo during the Clinton administration; was an attorney in New York City; and was a law clerk to Judge Roger Miner on the 2nd Circuit Court of Appeals.
Key life/career moments:
Gillibrand became a senator in 2009 to fill the vacancy caused by the resignation of Hillary Clinton when she was nominated by President Barack Obama as secretary of state.
In 2010, Gillibrand successfully campaigned to repeal the "Don’t Ask Don’t Tell" policy that banned gay men and lesbian women from serving in the military.
According to Gillibrand’s official website, she held the first Senate hearing on sexual assault in the military in almost a decade in 2013, as chairwoman of the armed services subcommittee on personnel. She also introduced the Military Justice Improvement Act, which "would remove sexual assault cases from the chain of command."
Her website also highlights her lead of a bipartisan coalition for the Campus Accountability and Safety Act, which would "hold colleges accountable for sexual assault on their campuses."
Where she stands on some of the issues:
Like other progressives in the Democratic field, Gillibrand supports the Green New Deal, Medicare for all, universal pre-kindergarten, bail reform and a $15 minimum wage.
Gillibrand announced that her campaign raised $2.3 million in the second quarter, with an average grassroots donation of $15. Her campaign closed out the second quarter of the year with more than $8.2 million cash on hand.
For Gillibrand, who has centered her campaign on fighting for reproductive rights, 65% of her online donors identified as women, according to the campaign.
Last quarter, Gillibrand raised $3 million, and transferred $9.6 million from her prior campaign committees. She ended the first quarter with $10.2 million cash on hand.
What you might not know about her:
According to FiveThirtyEight, Gillibrand was "among the least liberal members of the Democratic caucus" when she served in the House of Representatives, ranking 209th out of 241. However, in the Senate, she leaned more to the left and was the "seventh most liberal member of the 46-person Democratic caucus" in the last Congress.
She has voted against President Donald Trump’s positions "more often than any other senator" as of December 2017, according to FiveThirtyEight.
Gillibrand was the first senator to call on former Sen. Al Franken, D-Minn., to resign after he faced multiple allegations of sexual misconduct. In an interview with Self Magazine in 2012, she shared that she then had a standing weekly squash date with Franken.
Gillibrand published a children's book titled "Bold & Brave: Ten Heroes Who Won Women the Right to Vote" in 2018.
According to Gillibrand’s official website, she was "the first member of Congress ever to post her official daily meetings, earmarks and personal financial disclosures online."
She graduated in 1984 from the Emma Willard School in Troy, New York -- the first all-women’s high school in the United States.
ABC News' Adam Kelsey and Christopher Donato contributed to this report.