For some audiences, Vivek Ramaswamy is a biotech entrepreneur who pushed for pharmaceutical breakthroughs before he tried to break into politics. For others, he is a cultural warrior battling “woke” corporations or a crusader for his definition of “truth,” whether it be the sanctity of two genders or the perpetuation of fossil fuels.

The identity that the entrepreneur and Republican candidate for president has kept more or less under wraps since his undergraduate days at Harvard is another thing entirely, Da Vek the Rapper.

Yet there it was at the Iowa State Fair this month, the 38-year-old shape-shifting presidential candidate, microphone in hand, spitting Eminem’s “Lose Yourself” before a largely white crowd that appeared somewhere between amused and enthused. Beside him onstage was the Iowa governor, Kim Reynolds, who watched with the look of a mother baffled by her child’s latest science fair project.

As breakout moments go, Mr. Ramaswamy’s impromptu performance may not rise to the level of Bill Clinton’s saxophone solo on “The Arsenio Hall Show.” But it did separate him culturally from his generally more awkward and older competitors in the still-early race for the presidency.

The lyrics — “He opens his mouth, but the words won’t come out” — did not fit the fast-talking, quick-witted candidate in the slightest. The words “he knows when he goes back to this mobile home” do not exactly leap from a wellspring of personal experience for Mr. Ramaswamy, a multimillionaire entrepreneur with a middle-class upbringing, a $2 million mansion in the suburbs of Columbus, Ohio, and a largely self-funded presidential bid.

But rap and hip-hop are part of the Ramaswamy story, back to Harvard when his alter ego Da Vek rapped libertarian lyrics in all-black outfits down to a Kangol cap. As a freshman, he performed at an open mic before a Busta Rhymes concert, a moment that has since been exaggerated to make him Busta’s opening act.

He told The Harvard Crimson back in 2006 that “Lose Yourself” was his life’s theme song.

In an interview on Friday, Mr. Ramaswamy seemed a little sheepish about his return to rap. Theme song? “There are parts of what you say in the past that you recoil from,” he admitted.

But he did stick by his identification with Eminem, the unlikely white rapper from working-class Detroit who went on to become, by most measures, the best-selling hip-hop artist of all time.

“I did not grow up in the circumstances he did,” said Mr. Ramaswamy, the son of a physician mother and engineer father. “But the idea of being an underdog, people having low expectations of you, that part speaks to me.”

Eminem was, Mr. Ramaswamy said, “a guy in every sense who was not supposed to be doing what he did.”

The candidate said he did not plan to rap at Iowa’s center stage. Responding to a question that Ms. Reynolds had asked every presidential hopeful at her “fair-side chats,” Mr. Ramaswamy said his favorite “walkout” song for the campaign trail would have to be “Lose Yourself,” an unusual answer in this Republican field but hardly counterculture.

“Lose Yourself” was the centerpiece of “8 Mile,” the semi-autobiographical film in which Eminem plays an aspiring rapper struggling to prove himself in a largely Black subculture. The track took best original song at the Academy Awards in 2003, and the next year it won two Grammys, including for best rap song.

After his chat with Ms. Reynolds ended, Mr. Ramaswamy was signing autographs when an enterprising sound technician put the song over the loud speaker. The candidate raised his fist, lifted the mic to his mouth, and the rest is, well, not quite history but a nice moment.

Mr. Ramaswamy’s venture into hip-hop, a culture synonymous with Black struggle and triumphs, carried risks. Rhymefest, a Chicago rapper who defeated Eminem at a freestyle contest in 1997, noted that Mr. Ramaswamy had called Juneteenth a “useless” holiday and told CNN’s Don Lemon that Black Americans achieved equality only because they secured the right to bear arms, never mind that the Rev. Dr. Martin Luther King Jr. preached nonviolence and armed civil rights leaders like Fred Hampton were gunned down by law enforcement.

“It’s the rewriting and manipulation of Black history for Republican talking points that gets me,” Rhymefest said, adding: “Everyone has a right to music. Everyone has a right to express themselves through the culture that helped formulate their passions, and hip-hop is a passionate calling.” But, he said, “he doesn’t understand the words or the meaning.”

Soren Baker, a historian of rap, said such conflicts were nothing new for Republican politicians, who have tangled with artists since President Ronald Reagan drew the ire of Bruce Springsteen over “Born in the U.S.A.” in 1984.

Mr. Springsteen made clear he didn’t think the president was listening closely to his music’s often bleak portraits of Reagan’s America. Eminem has not commented on Mr. Ramaswamy’s performance. A representative did not respond to a request on Friday.

But it’s unlikely the rapper is a Ramaswamy fan. In 2017, Eminem famously performed a freestyle jeremiad against then-President Donald J. Trump, calling him “a kamikaze that’ll probably cause a nuclear holocaust.” Mr. Ramaswamy, in contrast, is steadfastly supportive of Mr. Trump, even as he runs against him for the 2024 G.O.P. nomination.

“What Vivek is doing is trying to align himself with the struggle of overcoming adversity,” said Mr. Baker, author of “The History of Gangster Rap.” “From what I know of Vivek’s policies, objectives and goals, they’re not in alignment with Eminem at all.”

Mr. Ramaswamy did not shy from the critique. “Is there a risk? There’s a risk in everything we do?” he said. But he added, “There’s no such thing as one rap community,” pointing to Ice Cube, the former leader of N.W.A who worked with the Trump campaign in 2020 on a Contract With Black America.

Of course, “Lose Yourself” is hardly a political anthem. It has become more like a frat house pregame rallying cry, or, as Rhymefest put it, “the song that gets the team out on the field.”

But Mr. Ramaswamy said it wouldn’t be blasting through his AirPods as he prepares to go onstage Wednesday at the first Republican primary debate of the 2024 cycle.

“I’m an adult,” he quipped.

Ben Sisario contributed reporting.