The 2020 Democratic primary’s historic field of women candidates just got a little smaller. On Wednesday, after failing to qualify for the September debate, two-term New York Sen. Kirsten Gillibrand announced that she was ending her candidacy.

It’s not hard to see why Gillibrand dropped out — the writing was on the wall. She still hadn’t met the donor threshold for the September debate, and had only hit 2 percent in one qualifying poll (she needed three more). Her debate performances didn’t do much to help her stand out from the other candidates — even on women’s issues, which she had made the centerpiece of her campaign. And although her name recognition rose over the course of the campaign, she didn’t become better-liked.

Her poll numbers barely shifted, too. In the month after she announced she was running for president, she hit a high of 3 percent in one February poll, but she never reached 3 percent again.

In the end, Gillibrand just couldn’t convince women voters — or most voters for that matter — that she was their candidate. But why her candidacy never picked up steam was always a little bit of a mystery. Of course, she had some hurdles to overcome. Like the other women running for president, she faced voters’ biases against women candidates. She also had the baggage of sparking Democratic Party heavyweights’ ire after she called on former Minnesota Sen. Al Franken to resign when sexual harassment allegations against him came out in 2017.

On paper, though, Gillibrand’s campaign didn’t seem especially quixotic. She was on the national stage for more than a decade before throwing her hat in the ring, and established herself as a strong advocate for women’s rights issues such as paid family leave and sexual assault in the military. She was also explicitly pitching her candidacy toward groups like white college-educated suburban women, whose political enthusiasm had just helped sweep a record-breaking number of women into office in the 2018 midterms.

So Gillibrand’s biggest problem may have simply been that there wasn’t a clear base for her in the Democratic electorate — at least not one for which there wasn’t also fierce competition in the rest of the primary field. After all, she was running against a number of other women who are also strong on issues like abortion rights and equal pay. Without another signature issue to help her stand out, she often got lost in the melee of the primary.

For instance, when several states passed laws dramatically restricting abortion in May, Gillibrand seemed like she could have had a breakthrough moment. She even traveled to two of the states to hold rallies in support of abortion rights, and she called for a federal law that would stop state legislatures from passing limitations on abortion — but so did Elizabeth Warren, Kamala Harris and even Cory Booker. In the second debate, Gillibrand tried again to seize the spotlight by taking Joe Biden to task for his position on a childcare tax credit in 1981 — but unlike Harris’s attack on Biden for his stance on school busing a month earlier, the moment didn’t really land.

In those moments and others, her rivals seemed to harness policies that were key to Gillibrand’s candidacy more effectively than she did. It was Harris, not Gillibrand, who grabbed headlines for her plan to penalize companies for failing to pay men and women equally. And in a recent Politico/Morning Consult poll, respondents said that Warren was best qualified to address gender equality, followed by Biden, Sanders and Harris — Gillibrand didn’t even crack the top 10.

In some ways, Gillibrand’s campaign may have also shown just how tricky outreach to women voters can be, even in a year where issues such as abortion and the #MeToo movement are prominent. Women make up about 60 percent of the Democratic base, but there isn’t a lot of evidence that they gravitate automatically toward female candidates because of their shared identity, or even because of shared priorities. In that Politico/Morning Consult poll, for instance, only 5 percent of Democratic women voters said that gender equality was a top voting priority. And Warren and Harris appear to be polling only very slightly better with women than men; that gap is actually bigger for Biden.

Finally, although Gillibrand said she had no regrets about calling for Franken’s resignation, it may have hurt her among donors and party elites. Her campaign at one point suggested that anger over her role in Franken’s departure was hurting her among major party donors. That may be true: Despite having been a formidable fundraiser in the past, she raised substantially less than others in the field. Moreover, unlike her fellow senators, who all drew the backing of political influencers from their home states, Gillibrand netted only one endorsement.

As the first woman to leave the race, Gillibrand’s departure is noteworthy, particularly since she could, in theory, have stuck around and tried to make it into the October debate — after all, the criteria to qualify isn’t changing. So her decision to drop out now may signal some strategic decision-making for candidates who are prominent within the party. and therefore have more to lose by staying in the race too long. It’s possible that even if the White House isn’t in the cards for Gillibrand this time, she may be thinking about running for another office, like governor of New York, and doesn’t want to fall out of grace with the party. Or she may be withdrawing with the goal of helping to pave the way for Harris or Booker — both of whom are friends.

The question now is whether other candidates follow Gillibrand’s lead. She is the sixth candidate to have dropped out this summer, and it’s possible that her departure could be a harbinger of more winnowing. Particularly for anyone else who is thinking about running for office in the future, and wants to stay on the Democratic Party’s good side by helping to narrow the field.