A Vanderbilt University poll conducted Oct. 8-13 showed Blackburn trailing former Tennessee Gov. Phil Bredesen, a Democrat, 49 percent to 37 percent among women registered to vote. The same poll found that men registered to vote favored Blackburn 50-37 percent, even as the broader poll showed the race is a tossup.
The stark gender divide, which has persisted in polling throughout the campaign, stands out in what has been described as the year of the female voter. Aware of the stakes as Democrats try to take control of the Senate, both candidates have intensified efforts to win over women as Election Day nears - vividly demonstrating that those voters are pivotal even in a deeply red state.
"Women are increasingly more liberal, and men are increasingly more conservative," said Amanda Clayton, an assistant professor of political science at Vanderbilt University. "That trend is becoming more pronounced and is likely to become more pronounced as it gets closer to the election."
Blackburn's tea party roots can appeal to conservative men who oppose traditionally liberal feminist candidates, Clayton said.
The push to confirm Supreme Court Justice Brett Kavanaugh, she added, may have given those men reason to look for women they could support, perhaps in response to more liberal women running for office.
Blackburn, the first female major-party Senate nominee from Tennessee, has previously demurred when talking about the groundbreaking aspects of her campaign. She said she isn't running on gender and has declined to answer questions about sexism she's encountered. When she was elected to Congress in 2002, she asked to be called "congressman" rather than "congresswoman."
But Blackburn's campaign has been willing to play the gender card.
In February, when some Republicans worried about losing a Senate seat encouraged retiring U.S. Sen. Bob Corker to reconsider, Blackburn's spokesman said anyone who thought she couldn't win the general election was a "plain sexist pig."
More recently, Blackburn herself has suggested a liberal bias on gender matters.
"Republican women are never going to get the attention that Democratic women are going to get," she said in a recent AP interview. "And you just expect that. I fully understand that Republican women do not fit the narrative that many in the media would like to construct. But I will tell you this: Most women, and you mentioned suburban moms, are very much like me."
Her campaign has emphasized her attempts to break the glass ceiling: the first woman hired by the Southwestern Company - a marketing business that sells educational materials - and the only Republican woman in the Tennessee Senate in 1998.
"Fighting against all odds is the story of her life," the narrator of one ad says.
Blackburn's team also has targeted Bredesen's handling of sexual harassment claims when he was governor.
In 2005, The Associated Press reviewed more than 600 workplace harassment investigation files collected when Bredesen was elected in 2002. The AP found that sexual and workplace harassment reports in 2005 were on pace to almost double from the previous year. Bredesen argued that reporting was up rather than the actual number of incidents.
Blackburn accused Bredesen of shredding records to cover up poor performance, but Bredesen called that a "total mischaracterization" and said he was trying to protect the privacy of those who complained.
And Bredesen's decision to support Kavanaugh has raised new questions about his support among women. The move appalled some Democrats, but others saw it as a way to win over Republicans in a state where he needs them.
In September, his campaign unveiled "Women United for Bredesen" - a group it says has roughly 50,000 Tennesseans aimed at providing a "space for women" to focus on their top issues.
Recently, pop superstar Taylor Swift broke her long silence on politics to endorse the Democrat. Swift said in an Instagram post that she wanted to back female candidates but could not support Blackburn because of her voting history on LGBTQ issues, opposition to the Violence Against Women Act and an equal pay law - saying bluntly that the congresswoman's voting record "appalls and terrifies me."
On the ground, Blackburn's core supporters say party loyalty will outweigh gender at the end of the day - though they don't always disconnect the two.
"She has set an amazing example, and in return, we are seeing more women running for office across the state," said Barbara Trautman, president of the Tennessee Federation of Republican Women. "We are very loyal to her."
Yet Bredesen is a looming threat, Trautman added, warning that voter turnout - particularly women - will be key.
"At this point, I'm not putting a lot of stock into polls," she said. "She's one of us, and we have high hopes."
Associated Press writer Jonathan Mattise in Nashville, Tennessee, and Washington Bureau Chief Julie Pace contributed to this report.
An earlier version of this report incorrectly said the poll was of women likely to vote, instead of women registered to vote.
Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.