Poll after poll in this election shows a huge gender gap has emerged – a major trend that underlines the crucial role women can play in November.

Most recently, a Quinnipiac poll in Michigan in late October found that 57 percent of women in the state supported Vice President Kamala Harris, while 40 percent of men did the same. Conversely, 56 percent of men supported former President Donald Trump, while 37 percent of women did. This has also been the case repeatedly in national polls. For example, a recent USA Today/Suffolk University poll showed Harris with a 16-point gap in the support she saw from men and women.

“It’s the battle of the sexes, and it’s not a game,” Quinnipiac pollster Tim Malloy said in a statement. “There is a glaring gap in Michigan and Wisconsin between the number of women supporting Harris and the number of men supporting Trump.” In Quinnipiac polls conducted in October in five of the seven key swing states, Harris had a significant lead among women, while Trump saw a similar advantage among men in those same places. (Quinnipiac has not released October results for Nevada and Arizona.)

Women supporting Democrats over Republicans is not a new phenomenon: members of the group have been more likely to support the party than men since the 1980s, and this political divide has only widened over time. This time, however, that split could have major consequences for the election outcome, due to the tightness of the race and other demographic shifts.

According to recent polls, Democrats appear to be losing support from groups they have relied on in the past, such as black men and Latino men. These losses could be offset by increasing turnout among women, especially since women are more likely to vote than men, and historically do so in greater numbers.

“The women’s vote will be decisive in this election,” said Katherine Tate, a political scientist at Brown University. “If Harris wins, it will be because women elected her.”

The gender gap is a sign of the progress Democrats have made over time

Women have now supported Democrats by significant margins in multiple cycles. In 2020, President Joe Biden won 55 percent of female voters, while Trump won 44 percent, and in 2016, former Secretary of State Hillary Clinton won 54 percent of female voters, while Trump won 39 percent, according to the Pew Research Center. If the actual outcome approaches the numbers pollsters see, Democrats could very well maintain these margins.

Part of Democrats’ growth among women comes from ideological shifts: A larger share of women across all age groups now identify as liberal, compared to two decades ago, according to a Gallup poll released in February . And younger women between the ages of 18 and 29 in particular are among the groups who are now much more likely to identify as liberal than in the past. Gallup found that 40 percent of young women identified as liberal in 2023, compared to 29 percent in 1999.

However, while the left is adding women, it is gaining few men. Over that same 24-year span, Gallup found that the share of men who identify as liberal across all age groups has remained relatively unchanged, with just 25 percent of young men identifying as liberal in 2023, up just 1 percentage point from 1999.

The leftward shift among women has been driven by a combination of factors, including backlash against misogynistic rhetoric from Republican leaders and allegations of sexual misconduct facing prominent political figures — such as Trump, who is the subject of more than two dozen allegations of sexual assault and misconduct , including a new accusation this week.

Social movements such as the #MeToo movement raised awareness about sexual misconduct and harassment in 2017. And women became more politically involved in the wake of Trump’s election, organizing through demonstrations like the Women’s March and running for elected office in record numbers.

Democrats’ positions on social issues, including reproductive rights, and outrage over the Supreme Court’s overturning decision Roe v. Wade in 2022 have also resonated with some women. Trump was responsible for appointing the judges who led the overthrow of the presidency Rooand has bragged about his role in it. Democrats, meanwhile, have established themselves as the party committed to defending reproductive health care.

Since the 1980s, many women have increasingly come to see Democrats as people who also operate in their economic interests, historian Suzanne Kahn of the Roosevelt Institute wrote for Time. That idea can be traced back to President Ronald Reagan’s decision to cut social benefits such as Social Security and Social Security, a reduction that disproportionately harmed women, Kahn wrote. And since then, this situation has been exacerbated by efforts by Presidents Barack Obama and Bill Clinton to pass laws addressing the gender pay gap and establishing family leave.

“Women believe they or their families need help or protection from the government,” said Democratic pollster Celinda Lake. “Men consider it a good day when the government doesn’t do anything bad to you.”

And Democrats have been able to take advantage of the power of representation as the party has diversified as well. The Democratic Party itself has become more representative of women in recent decades and has made a successful effort to recruit and promote female candidates, something Republicans are still catching up on.

In the House of Representatives, for example, 43 percent of Democratic lawmakers are women, while 15 percent of Republican lawmakers are women. The party’s efforts have also put two women at the top of the list of Democratic presidential candidates, including Harris, something that many Democratic voters have expressed enthusiasm about.

Women’s shift to the left has created a party affiliation with Democrats, Lake says, and that could have major consequences this election cycle.

Right now, some swing state polls are even split between the two presidential candidates — and increasing support for women could push Harris over the top.

“In close races, the formula for victory is to win women by more than you lose men,” Lake tells Vox.