DES MOINES — As she nears a verdict from voters in Iowa, Sen. Elizabeth Warren is leaning in on gender.

Warren used a spat with Sen. Bernie Sanders, I-Vt., to assert that the female candidates on Tuesday's debate stage were the most electable against President Donald Trump. She approached Sanders afterward to accuse him of calling her a "liar" as cameras rolled.

She added a "fireside chat" with activists for Planned Parenthood Action Fund in Des Moines to her schedule Saturday. She picked up a key endorsement from Janet Petersen, the highest-ranking woman in the Iowa legislature, who on Sunday cited Warren's plans to improve maternal health care as the reason she sided with her.

At the Planned Parenthood event, the senator from Massachusetts defined the election's stakes as she saw them: "To have an America where women are really secure, where access to health care is safe and readily available ... we need to have women representing us and we need to have people who are sympathetic to women representing us in all parts of our government in all states across this country. That is our mission."

Warren, the sole female candidate among the campaign's front-runners, paid special heed to women who have flooded politics since the defeat in of Hillary Clinton, the first female nominee of a major party.

"This is not 2016, and look - I was out there in 2016, and I know how many other people were, too," she said. "It didn't work, but it was a big, big wake up call for a lot of people. And that's why I say, the world has changed. So now the question is, what are we going to do about it?"

The focus on gender this weekend coincided with the third anniversary of the Women's March, which included demonstrations in Iowa. The initial marches represented the first angry blast of female energy against Trump in the wake of his victory over Clinton, power that fueled a huge turnout of women in the 2018 midterm elections and pushed a record number of women to victory in House contests.

Yet Warren's gender strategy is risky: This year, Democratic voters have shown little interest in reaching for history as they did in 2016, instead painstakingly calculating which candidate delivers the best odds of beating Trump.

Two Democratic presidential candidates who put gender at the center of their messages - Sens. Kirsten Gillibrand of New York, and Kamala Harris of California - failed to gain traction over the past year. Another female senator, Amy Klobuchar of Minnesota, has struggled to join the top tier of candidates, even in next-door Iowa. All, like Warren, have fought against voter fears that replicating the party's 2016 choice would lead, again, to Trump's victory.

"Voters are terrified of anything that looks or feels similar to 2016," said Meredith Kelly, a former aide to Gillibrand, who left the race last summer amid tepid support. "Because of that almost blinding fear, there are more barriers to cross as a female candidate in this race."

Warren surrogates acknowledge the difficulty.

"Half of this country are women, so it's important that our elected officials look more like our country," Rep. Deb Haaland, D-N.M., a Warren surrogate, said in an interview before she introduced Warren onstage in snowy Newton, Iowa. "We need that true representation."

Sen. Elizabeth Warren addresses the crowd in Newton, Iowa, on Jan. 17. Jabin Botsford / The Washington Post
Sen. Elizabeth Warren addresses the crowd in Newton, Iowa, on Jan. 17. Jabin Botsford / The Washington Post

About voters' apparent anxiety about another female nominee, Haaland sounded resigned.

"That doesn't escape me, trust me," Haaland said. "It doesn't escape me at all."

Warren has made an overt connection throughout the campaign between her candidacy and the triumphs of earlier women - far more noticeably than did 2016 nominee Clinton.

She has delivered three major speeches rooted in the stories of women who pressed for historic change, including an address in New York centered on the rise and influence of former labor secretary Frances Perkins after the Triangle Shirtwaist factory fire.

In that speech, Warren stood before an audience of about 20,000 below the marble arch in Washington Square Park and said bluntly: "We're not here today because of famous arches or famous men."

A speech in Atlanta in November, Warren said black washerwomen who led a successful strike in the 1880s for higher wages proved "the women stood together." In a New Year's Day speech in Boston centered on Phillis Wheatley, the first black woman to publish a book of poetry in the United States, Warren urged voters to "imagine" a better country where more is possible.

In her stump speech, Warren likes to outline executive actions she would take immediately and introduces the riff by saying, "I will do everything a president can do on day one, all by herself."

She also frequently points out that she was told in 2012 that a woman couldn't beat popular Republican incumbent Sen. Scott Brown of Massachusetts. (She did.)

Her campaign's gender tweaks are hardly subliminal. A surrogate handed out jars of nail polish specially made to match the campaign's signature "liberty green" hue - the color of the Statue of Liberty. Her walk-on music? The theme from "9 to 5," the movie in which three mistreated women workers take revenge on their abusive male boss.

The highest-profile gender play, however, occurred on Tuesday's debate stage, when Warren confirmed a CNN report that Sanders, in a private meeting with her in 2018, had told her he thought a woman could not defeat Trump. Sanders has heatedly denied making that statement.

Video: Bernie Sanders 1988 C-SPAN interview addressing a woman being president

Some watching embraced her argument that it was the women onstage who represented the best chance of victory in November.

"Her goal was to use this as an opportunity to make a best electability argument she can, which I thought she definitely did," said Jennifer Palmieri, a former top aide to Clinton in 2016 and author of "Dear Madam President: An Open Letter to the Women Who Will Run the World."

"In doing so she had an opportunity to strike a chord with women who know what it feels like to be doubted and undermined even by a friend," Palmieri said. "And that's a pretty powerful thing."

Success by Warren would mean reversing the experience of the other women in this year's class of presidential candidates.

Sens. Kamala Harris, D-Calif., and Kirsten Gillibrand, D-N.Y., speak near the stage at Rep. James Clyburn's World Famous Fish Fry in Columbia, S. C., last June. Melina Mara / The Washington Post
Sens. Kamala Harris, D-Calif., and Kirsten Gillibrand, D-N.Y., speak near the stage at Rep. James Clyburn's World Famous Fish Fry in Columbia, S. C., last June. Melina Mara / The Washington Post

Harris designed her campaign logo as an homage to Shirley Chisholm, the first woman to run for the Democratic Party's presidential nomination. Gillibrand adopted a hot-pink campaign motif, and made women's empowerment her central theme.

But both campaigns learned early that 2020 would not be like 2018, the banner year for Democratic women.

From focus groups, polling and front-door talks with voters, the Harris campaign repeatedly confronted voter concern about the electability of a female candidate against Trump. The Gillibrand campaign also heard in focus groups from potential Democratic voters worried that their neighbors would not support a woman for president, even as they said they would.

"One of Trump's impacts on this election is those conversations on electability have really dominated," said Lily Adams, who served as a top Harris aide. "That really wasn't a conversation in 2016, when I worked for Hillary."

Both campaigns built specific strategies in Iowa to try to turn out women energized by Trump's victory - many of whom, according to the campaigns, were new voters who had never participated in the caucuses. Gillibrand spoke at the Women's March in Des Moines last year as she sought to woo that support.

By the end of her campaign, Harris had shifted her tone from one of empowerment and transcendence to a more defensive posture. She openly talked about bias against women and minority candidates, and encouraged her supporters to "be brave."

Harris was especially aggressive in reaching out specifically to women angered by the rise of Trump, making what her campaign called "blue-wave women" a focal point of her Iowa organizing strategy.

Warren's team has hired some of Harris's staffers in Iowa, and hopes to pull off what the senator from California could not, even if some voters are not sure that is possible.

Meghan Davis leaned against a wood-paneled wall at a standing-room-only town hall for Warren on Friday and pulled a fistful of hot-pink yarn from her tote bag. She had just 17 days to complete two goals: finish knitting a pink pussy hat to wear to the caucuses and decide who she'll support when she gets there.

Although she planned to wear the hat that has become the symbol of female resistance to Trump, she found herself torn between Warren and Pete Buttigieg, the former South Bend, Indiana, mayor.

"My thought was 'Oh, I love her, but she doesn't really have a chance,' " said Davis, a Presbyterian pastor. Part of the hesitation, she said, is that after 2016 she sensed that "the deck is stacked against female candidates."

This article was written by Michael Scherer, Annie Linskey and Holly Bailey, reporters for The Washington Post.