IOWA CITY, Iowa — Democratic voters say that more than anything, they want to beat President Donald Trump in 2020. But some worry that means putting their hope of electing the first woman president on hold.

"I can hardly think about it. It makes me sick thinking about how nasty this could get for a woman,” Marianne Mason said, clutching her stomach as she waited for Sen. Kamala Harris of California to arrive at a town hall event at the University of Iowa on a recent Wednesday night. "How are they supposed to rebut someone like Trump? I want to see a woman in the White House, I really do. But I just don’t know if it can happen against him."

Mason, 67, of Iowa City, is not alone in her thinking. In conversations with dozens of Democratic primary voters — men and women — across several states, voters told NBC News that Hillary Clinton's loss in 2016 made them rethink how willing Americans are to vote for a woman for president, especially when pitted against Trump. For some, the risk of four more years of a Trump presidency is not worth another attempt to break the final glass ceiling for women.

Although many of these voters said they recognize that the "electability" question is often unfairly aimed at women running for office, they stressed the need to be realistic about an electorate they view as sexist and a president who they say is only too eager to launch gender-based attacks.

Sen. Kamala Harris, at the University of Iowa on April 10, leads in the polls among the Democratic women running for president, but trails three white men: Joe Biden, Bernie Sanders and Beto O'Rourke. Charlie Neibergall / AP file

"I think against Trump any woman is going to have difficulty with electability, that’s just kind of a reality we have to contend with," said Emily Van Kirk, 22, at a West Des Moines campaign event with Sen. Elizabeth Warren of Massachusetts in March. “We need to make sure we are making an informed decision about who is actually going to be able to combat the things he says that are not only derogatory but just ignorant about women.”

Shirley Ehlers, a retiree from Perry, Iowa, who has been active in women’s political organizations in her community, agreed.

“We have Trump for president, and that says a lot," Ehlers said. "That shows a disrespect in this country for women at a lot of different levels. I think we need to address that first before a woman can win."

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Democratic strategists say they recognize that many voters are haunted by the 2016 election. Polling data shows an unusually large number of Democratic voters say electability takes priority over values, compared to previous elections. Fairly or unfairly, strategists say, the electability question is one female candidates must answer, and they will have to convince voters that they are just as capable — or more — of defeating Trump as any of the men in the race.

"Right now there is this fear and concern that we have to pick the safest candidate," said Adrienne Elrod, former director of strategic communications for Clinton's 2016 campaign. "Unfortunately, that caution does transition into, 'Can a woman take him on?'"

Such caution, Elrod and other strategists say, is reflected in early polling, which consistently shows men dominating the primary field, even among a historic number of female candidates. In an average of polling data compiled by Real Clear Politics, former Vice President Joe Biden, who announced his candidacy on Thursday, leads the pack with roughly 30 percentage points, followed by Sen. Bernie Sanders of Vermont at 22.5 points and former Rep. Beto O'Rourke of Texas at 8.8 points. All three are white men. Harris, at 8.5 percent, currently polls the highest on average out of the women running.

Early polls can often be a reflection of name recognition, which could explain such big leads for Biden and Sanders. Nevertheless, Democrats say the numbers still capture the challenges that women will face with primary voters who consistently say that their top priority is electability.

On the campaign trail, female candidates come prepared for the “can you actually beat Trump” question, often citing their experience.

Warren, for example, frequently emphasizes her decisive win over Republican Scott Brown in her first race for Senate. Brown was elected to the Senate in a 2010 upset victory over Martha Coakley, then the Massachusetts attorney general.

Coakley's loss had some Democrats running scared, Warren remembers.

"When I thought about jumping into the race, I heard this over and over again: ‘Don’t run. A woman can’t win here. Not yet,'” Warren wrote in a March fundraising email to supporters. "I heard from a lot of women who were afraid that it would be too painful to see another one of us go up against him and lose."

Sen. Kirsten Gillibrand of New York referred to her first campaign in 2006 when she was elected to Congress after defeating Republican Rep. John Sweeney in a competitive district.

“Senator Gillibrand is the only Democratic presidential candidate in the field who has beaten a Republican incumbent in Republican territory, and she did so by going toe-to-toe with a loudmouth bully,” Evan Lukaske, a spokesperson for Gillibrand’s campaign, said in an email to NBC News, noting the “unique parallel to the presidential contest.”

But some Democratic strategists caution against reading too much into electability concerns.

“I think the question is typically thrown at candidates we are not used to,” said Christina Reynolds, a spokesperson for Emily's List, a PAC that supports female candidates who back abortion rights, and a former campaign staffer for Barack Obama and Hillary Clinton.

Reynolds noted that Obama was considered "unelectable" heading into the 2008 election — until he won the Iowa caucus.

“We actually saw it thrown at Donald Trump because he was not a typical candidate, but he won. I would argue voters should throw out electability and vote for who you like,” she added. “We are — as a country, as individual voters — we are not always great at predicting who is electable.”

Reynolds and other Democrats also point to the 2018 midterms, when women were elected to office across the country at record levels, as evidence that the general election electorate could be more open to voting for a woman than some assume.

"What voters are doing now is kicking the tires of each and every candidate, and they are taking the role of selecting this nominee very, very seriously," Patti Solis Doyle, who managed Hillary Clinton’s 2008 campaign, said in a phone interview with NBC News. "I think, however, when they say that a woman can't beat Donald Trump, I just don't believe that to be true. If you look back at the last election of 2018, not only did more women run than ever before, but more women won than ever before."

Some academics argue that success on the congressional and state level does not necessarily translate into success on the presidential level.

"Women do quite well politically when they are perceived as being in service positions and wanting to have power as much as in that they will be serving a local constituency," said Kate Manne, a philosophy professor at Cornell University who has written extensively about gender and politics. "Problems arise when women are trying to run for the presidency, because that is the ultimate masculine-coded authority position and one is subordinate to no one."

And political science research suggests that voters may not be reading too much into the 2016 results, either. Political scientists John Sides, Michael Tesler and Lynn Vavreck explored this issue in-depth in “Identity Crisis,” and found that Clinton’s gender was a vulnerability in 2016.

“The total impact of Clinton’s gender is impossible to measure,” they write. “Nevertheless, it appears that she was hurt more by gender than she was helped,” adding that the “2016 campaign appeared to activate modern sexism, especially among white men.”

Some Democratic primary voters clearly learned this lesson. As Sharon Quinn, 70, of Scranton, Pennsylvania, put it at an O’Rourke campaign event in March: “We need someone who the boys will vote for, OK?"