The congresswoman's performance among women came out a wash because those 45 and older favored Blackburn by 9 percentage points, while women younger than that backed Democratic former Gov. Phil Bredesen by 10 points, according to data gathered by AP VoteCast, a nationwide survey of 115,000 voters and 22,000 nonvoters.
Blackburn, a fiery supporter of President Donald Trump, was elected Tuesday to replace frequent Trump critic Bob Corker, who is retiring.
Pre-election polls suggested it was an open question whether female voters would back Blackburn, who firmly endorsed Trump's choice of Brett Kavanaugh for the Supreme Court when the nominee faced a woman's sexual assault allegations dating from high school.
While Kavanaugh denied the allegations and was confirmed last month, the nomination fight brought gender to the forefront of Tennessee's $85 million Senate contest. Bredesen broke with Democrats in ultimately saying he would have voted for Kavanaugh, but he tempered that by calling Kavanaugh's accuser a "heroine."
Some polls suggested Blackburn would struggle, while others suggested female voters were more divided.
Age overall represented a big breaking point for Blackburn, with both male and female voters 45 and older favoring her by 18 percentage points, and those younger leaning toward Bredesen, 51 percent to 46 percent. Men, meanwhile, preferred Blackburn over Bredesen by 20 points.
Bredesen got a campaign boost from Taylor Swift. The pop star endorsed him on Instagram and criticized several of Blackburn's votes on LGBT and women's issues, saying her voting record "appalls and terrifies" her.
But immigration was the issue foremost on voters' minds, the survey showed.
Regardless of gender, voters who supported Blackburn, like voters who supported Republicans nationally, focused on immigration: Nearly 4 in 10 Blackburn voters named immigration as the most important issue confronting the nation. About the same share of Bredesen voters identified health care as the key issue.
Blackburn, a Fox news regular with tea party credentials, followed Trump's lead on immigration in touting his proposed U.S.-Mexico border wall and echoing Trump's fear-instilling rhetoric about thousands of Central American migrants headed north across Mexico.
"There was a lot of agreement on issues and I think that that's why women moved toward us," Blackburn told The Associated Press in a phone interview.
Among women 45 and older, 55 percent described themselves as Republican or leaning that way, with 35 percent saying they lean or are Democratic. For women up to 44 years old, 47 percent said they lean or are Republican and 43 percent said they lean or are Democratic.
Blackburn made a point of stressing she wasn't running for office on her gender. But she picked moments to bring gender into focus.
She preferred to be called congressman, not congresswoman. And in her victory speech Tuesday, she happily said people could now just call her senator.
Her campaign also highlighted her moves to break the glass ceiling: She was the first woman hired by a major Nashville-based marketing and publishing company that sells educational materials - and the only Republican woman in the Tennessee Senate in 1998.
In February, when some Republicans worried about losing a Senate seat encouraged Corker to reconsider, Blackburn's spokesman said anyone who thought she couldn't win the general election was a "plain sexist pig."
Still, the historic significance of becoming Tennessee's first female senator wasn't lost on her on election night. She specifically noted a moment when a group of jubilant college-aged women came up to her at her victory party.
"They were just so excited that there was a female that they identified with who was breaking a barrier and opening more doors for them," Blackburn said. "And I appreciate having that opportunity."
As for Swift, Blackburn said, she doesn't think her interjection made any difference one way or another.
AP VoteCast found that among Blackburn voters, 55 percent said they have an unfavorable view of Taylor Swift and just 16 percent have a favorable one. Among Bredesen voters, 51 percent have a favorable opinion of Swift and just 10 percent have an unfavorable one. The remainder of both groups of voters did not give an opinion.
"I hope (Swift) and her colleagues could kind of shake it off and realize that I always like to have a conversation with people who want to improve the quality of lives for Tennesseans," Blackburn said, throwing in a reference to Swift's 'Shake it Off.'
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