After a stint as the Democratic primary front-runner, Sen. Bernie Sanders’s revolution is rapidly stalling. After a series of surprising losses on Super Tuesday, he lost again in Michigan earlier this week, despite spending days campaigning across the state.

In contest after contest, Sanders has struggled to make inroads with key Democratic constituencies — in particular, black voters and older voters. But there’s another trend that’s plagued him throughout the primary: He does poorly with women. According to aggregated exit polls from the states that have voted so far, Sanders’s support is 8 points lower among women than his support among men.

Sanders consistently gets less support from women Vote share by gender in entrance and exit polls from completed state primaries and caucuses, by candidate Sanders Biden State Men Women Diff. Men Women Diff. Iowa 26% 20% -6 16% 16% 0 New Hampshire 31 23 -8 8 8 0 Nevada 38 30 -8 18 17 -1 South Carolina 24 17 -7 48 49 +1 California 38 32 -6 19 28 +9 Texas 34 27 -7 33 33 0 North Carolina 27 21 -6 42 42 0 Virginia 29 19 -10 49 57 +8 Massachusetts 31 26 -5 34 34 0 Minnesota 37 25 -12 39 41 +2 Tennessee 27 23 -4 38 44 +6 Alabama 20 14 -6 61 65 +4 Oklahoma 30 21 -9 40 37 -3 Maine 38 29 -9 29 37 +8 Vermont 53 51 -2 24 20 -4 Washington 41 27 -14 28 36 +8 Missouri 38 32 -6 56 64 +8 Mississippi 18 12 -6 78 83 +5 Source: Edison Research

Sanders has consistently been at a disadvantage among women in this year’s primary. And that’s not a deficit that a Democratic primary candidate can simply ignore, since women make up a majority of the party’s electorate this year — 57 percent of primary voters so far.

“Consistently having lower support among women is a problem of optics because it makes it look like there’s something going on that prevents women from backing you,” said Kelly Dittmar, a political scientist at Rutgers University–Camden who studies gender and politics. “But it’s also an actual numbers issue because men are just a smaller proportion of the Democratic electorate. You need to do well among women in order to win the nomination.”

It’s hard to pin down a single reason why men seem to be more attracted to Sanders’s candidacy than women. There isn’t really evidence, for example, that Sanders is especially likely to attract supporters who display hostile feelings toward women. In a recent analysis, researchers for Data for Progress did find that gender bias kept some voters from supporting Warren — but Sanders’s supporters didn’t hold more sexist views than Biden’s. But there is evidence, according to an analysis by Dan Cassino, a political science professor at Fairleigh Dickinson University, that while support for Biden increases among voters with more sexist views, those with the most sexist views were disproportionately likely to favor Sanders. And sexism was higher, in general, among men.

“Educated Democrats who are quite sexist are disproportionately likely to be Sanders supporters,” said Cassino. “To be clear, there aren’t a lot of those people in the Democratic Party. But because of their education and social capital, they’re probably more inclined to tell people about their views and express them online.”

This doesn’t explain all of Sanders’s struggles with women. But his lopsided support among this group provides a window into some of the divisions that are roiling the Democratic primary electorate this year — particularly the limits of Sanders’s lefty, anti-establishment message and the aggression of his supporters at a moment when many Democratic voters are laser-focused on finding a candidate who can beat Trump.

At a Biden rally in Detroit last week, Mary Mckenney, 69, said that she hadn’t made up her mind about which candidate to support until the race narrowed to Biden and Sanders. Then, she said, her choice became very clear. “It’s not even that I don’t like Bernie’s ideas, I just think they can’t happen,” she said. “And I think if he’s the nominee there will just be more fighting and conflict. We need someone who can bring Democrats together.”

Views like Mckenney’s aren’t universal among Democratic women. Plenty of women are enthusiastic about Sanders — including Mckenney’s daughter Carrie, 43, who was standing next to her at the rally. But older women like Mckenney make up a much bigger share of the Democratic electorate, which makes them a disproportionately important group. So far, women over the age of 45 have made up 38 percent of Democratic primary voters, while women under the age of 45 only made up 19 percent. And the age gap that has emerged across the primary is almost certainly shaping women’s support for Sanders too: older women tend to be more moderate than younger women, which means they may be less likely to see Sanders’s calls to upend the status quo as feasible or appealing.

But generational fissures aren’t the whole story. Women of all ages told us they liked Sanders’s ideas but found aspects of his candidacy alienating. “I don’t have the same aversion to the DNC and the Democratic establishment that a lot of Bernie supporters seem to have,” said Tiffany Keane Schaefer, 31, who lives in Chicago and volunteered for Warren but is now undecided about who she’ll support. Schaefer told me she’s disturbed by some of the criticism Sanders allies levied against Warren for not endorsing Sanders after she dropped out. “Right now it feels like I am getting blasted every single day on social media about why Warren isn’t doing enough to help Sanders.” That antagonism makes Schaefer feel uncomfortable about the prospect of supporting Sanders, even though she’s closer to him on the issues than to Biden.

One of the central messages of Sanders’s campaign is the need to take on the political establishment — including the party whose nomination he is seeking. On the day before he won the Nevada caucuses, Sanders tweeted, “I’ve got news for the Republican establishment. I’ve got news for the Democratic establishment. They can’t stop us.”

That kind of message obviously appeals to people who are disaffected with the Democratic Party — but to people who don’t have a problem with the party, it can seem like an unnecessary risk. “I understand why the young people love Sanders — student debt, it’s a real problem,” said Grace Andrews, 79, who was waiting outside the Biden rally in Detroit with her grandson. “I just have a concern that he is not willing to make the compromises that are necessary in our political system, or work with people in the party who may not share his views.”

Women are especially likely to say that being a Democrat is an important part of who they are. According to our analysis of a Democracy Fund + UCLA Nationscape survey of likely primary voters administered from Feb. 20 to Feb 26, 63 percent of Democratic women say that their party affiliation is somewhat or very important to their identity, compared to 58 percent of Democratic men. That’s not an enormous difference, but it is statistically significant — it also lines up with other research that finds partisanship functions as a more important social identity for women than it does for men. Women over the age of 45 are especially likely (67 percent) to say being a Democrat is an important part of their identity.

Of course, not all women are turned off by the idea of radical changes to the system — including radical change to their own party. “It just feels like the Democratic Party has forgotten what it means to be the party of the working class,” said Diana Post, 30, who lives in Detroit and said she was torn between Warren and Sanders until Warren dropped out of the race. She now describes herself as a “big Sanders fan.” “We need someone more radical than what the establishment is putting forward, a candidate who can shake things up.”

Over the course of the primary, voters have been asked if they would prefer a candidate who agrees with them on the issues or a candidate who can beat Trump. According to the exit polls so far, women are likelier to be in the latter category: 65 percent of women say they would prefer a candidate who can defeat Trump, compared to 59 percent of men. That isn’t an overwhelming gap, to be sure, but it’s still noteworthy given that women make up a disproportionate share of the Democratic electorate. And in the primaries so far, voters who prioritize a candidate who can defeat Trump are disproportionately likely to support Biden.

That was where Ruth Vail, 77, said she had landed. She was standing on the University of Michigan quad, waiting with her 15-year-old grandson Leo to hear Sanders speak. But even though she was curious to hear what Sanders had to say, she said she’d probably be voting for Biden. “I think unfortunately it’s just going to be very easy to paint Sanders as an extremist, someone who’s a scary person who wants to change everything,” she said. “And I really just want a president who won’t keep me up at night, thinking about what he’s going to do next, thinking about who he’s going to appoint to the Supreme Court. The most important thing to me in this election is just ensuring that Donald Trump is no longer our president.”

Laura Bronner contributed research.