DETROIT—Vice President Kamala Harris sent out Grammy award-winning singer Lizzo, clad in suffragist white, to jazz up a crowd gathered in a high-school gym here Saturday, before many of them cast their ballots early.

When Harris took the stage, she called Lizzo “phenomenal” and ticked through record-breaking early-voting data from some states. Then the music-loving vice president put her right hand on her hip and made a quip.

“Now who is the capital of producing records?” she said, smiling broadly at her Motown joke.

The crowd pleaser was the latest musical reference aimed at showcasing a more personal side as the Democratic nominee races to overcome a central challenge of her candidacy: Many voters say they still don’t know her. Throughout her career, she has appeared guarded and changed her stance on some issues. Her unexpected ascent to the top of the presidential ticket months before Election Day has made for a rushed introduction to the electorate.

Harris, who turns 60 on Sunday, has worked in recent weeks to fill out that picture by parceling out details of her life and insights into her personality during interviews and smaller campaign stops. She surprised some of her own allies by calling herself a gun owner in the presidential debate. The vice president described making french fries during a college summer job at a McDonald’s. She told voters that she collects vinyl records with her stepson and that she watches Formula One auto racing.

Nearly one in five voters said they need to learn more about Harris’s career and policy positions, according to a recent Wall Street Journal poll of voters in the seven swing states. Among the independents who are most important in determining the election’s outcome, nearly 40% said they need to know more, the poll found.

Young voters also pose a problem: More than a quarter of Gen Z voters said they need to know more about her, according to the survey.

This poses a potential liability for her candidacy given the flood of negative advertisements that Republicans are rolling out in an effort to define her in the campaign’s final stretch. Former President Donald Trump , by contrast, is well known to voters not just from his presidency but from thrusting himself into the spotlight for decades.

Tabloids brimmed with Trump’s antics in the 1980s and 1990s, and a feature film on this period of his life is playing now in theaters. His gift for showmanship landed him on network television. An NBC reality show, “The Apprentice,” featured Trump from the early 2000s until he started running for president in 2015, bolstering the idea that he is a successful businessman. The real-estate tycoon relished the attention and displayed a knack for grabbing unscripted moments.

Democratic presidential nominee U.S. Vice President Kamala Harris poses for a selfie with a supporter during a campaign rally at Riverside Park in Grand Rapids, Michigan, U.S, October 18, 2024. REUTERS/Kevin Lamarque

Harris has said she isn’t always comfortable putting her personality on display. “It feels immodest to me to talk about myself, which apparently I’m doing right now,” she told the radio host Howard Stern in a recent interview. To the radio host Charlamagne tha God, she acknowledged the problem she faces: “Some people are just getting to know me.”

Her critics say she is overly scripted on the campaign trail, a notion bolstered during the early weeks of her candidacy when she avoided interviews. “That would be called discipline,” Harris responded when Charlamagne tha God needled her on her tendency to stick to her lines.

During a blitz of public appearances in recent weeks, she has been carefully doling out more personal details. She told CBS News’s “60 Minutes” that her firearm is a Glock and that she has used it at a shooting range. During a recent fundraiser in Arizona, she meditated a bit on her leadership style. “I don’t want any ‘yes’ people,” Harris said.

In particular, she has detailed her tastes in music. Favorite Bay Area artists include Tupac Shakur and Too Short, she said on the “All The Smoke” podcast. She singled out the Prince album “1999” as “spectacular” in her conversation with Stern, and told the late-night host Stephen Colbert that Aretha Franklin and Eminem are among her top artists with Michigan ties. To Justin Carter of “The Shade Room,” she revealed that she is in touch with the mother of Beyoncé, Tina Knowles. “She’s been supporting me for years,” Harris said.

Harris collects vinyl records, a passion she now shares with her stepson, Cole Emhoff, she told Stern. “Wherever I am, I try to swing into the record store,” she said. “And then I’ll pick up vinyl for him and bring it back for him.” A few days later, she stopped at Legenderie Records & Coffee House, where she purchased a Marvin Gaye record.

She isn’t a golfer, but she does watch Formula One with her family, she has revealed in recent weeks. Her favorite driver is Lewis Hamilton, the Briton sponsored by Mercedes-Benz.

She works out every morning, she said during several recent interviews. The routine can be 30 to 45 minutes on an elliptical machine, and she passes the time by watching MSNBC’s “Morning Joe.” She enjoys family-size bags of Doritos and sipped a beer with Colbert. The beverage sets her apart from Biden and Trump, neither of whom drink alcohol.

The challenge Harris faces was apparent to some of the supporters who gathered in Lansing, Mich., at a union hall Friday to hear her. “For four years I don’t think she was out there engaging the base,” said Aaron Nowland, president of the International Brotherhood of Electrical Workers Local 665. “Did they get to hear what she was saying each week? No.”

Several others in the audience said that as they were phone-banking for Harris, they found younger voters to be a particular challenge, largely because they are consuming so much news through social media and aren’t reading political articles. One person lamented that if Harris could package all of her ideas and personality into a videogame, she would break through more effectively with the younger generation.

And unlike most Americans, who feel they know Trump, the vice president told voters at a Univision town hall that she doesn’t.

“I only met him one time,” she said. “On the debate stage.”

Write to Annie Linskey at annie.linskey@wsj.com