J.D. Vance, an Army veteran who grew up poor and suffered from imposter syndrome, entered Yale Law School not looking as if he was destined to become President of the United States.

Many who know him attribute his extraordinary success story to the influence of his wife, Usha Vance, whom he met on an Ivy League campus.

By any measure, 40-year-old J.D. Vance is on a meteoric rise. In just three years, he went from a long shot running for the Senate to the third youngest vice president in U.S. history.

At his side every step of the way is his "spiritual guide" whom he calls his wife Usha.

The two began as friends at Yale Law School. Although they shared a reading group and social circle, their backgrounds were very different.

The daughter of Indian immigrants, Usha Vance, 39, grew up in a suburb of San Diego before pursuing undergraduate and graduate degrees at Yale University.

Her husband grew up in Middletown, Ohio, and was born into a family in the impoverished Appalachian Mountains of eastern Kentucky.

Charles Taylor, a classmate at Yale and a friend of the couple, told the BBC that their contrasting upbringings were what drew them to each other.

"They're always made up of very different people," he said.

In his 2016 best-selling memoir, Hillbilly Elegy: A Memoir of a Family and Culture in Crisis, J.D. Vance recounted how his wife helped him adjust to life at a top law school.

“I have never felt uncomfortable in my life,” he wrote. “But I did it at Yale.”

In the book, the vice president-elect describes an instance when his wife taught him which cutlery to use for which part of a formal meal, picking silverware from the outside to the inside.

“Usha was teaching JD about the subtle aspects of attending an elite institution,” Taylor recalls. “Usha was his guide throughout the process.”

The book explores his personal experiences with poverty and drug addiction among the rural lower classes, while also providing a glimpse into the Vances' relationship.

When J.D. Vance was revealed as Trump's running mate in July, his profile was limited.

He is a junior senator from Ohio who was first elected to public office two years ago after a career as a Marine, lawyer and venture capitalist.

She is a highly accomplished attorney who clerked for Supreme Court Chief Justice John Roberts and Court of Appeals Judge Brett Kavanaugh before being appointed to the U.S. Supreme Court by Trump.

Usha Vance was a corporate litigator at Munger, Tolles & Olson, a prominent law firm in San Francisco and Washington, D.C., before quitting to help her husband run for vice president.

Jai Chabria, a family friend and political consultant, told USA Today that the couple is "a team in every way."

"When he would go out and give great speeches, she would advise him and give him her opinions, and they would be taken seriously," Chhabria said.

The mother of three has played a behind-the-scenes role since her husband became Trump's running mate.

Friends say she shunned the spotlight in part because she wanted to protect their children, ages seven, four and three.

Usha spoke publicly several times during the campaign, including in an interview with Fox News and when introducing her husband at a party conference.

That speech gave perhaps the clearest public view of their marriage.

“It’s safe to say that neither JD nor I expected to be in this situation,” she said.

Taylor said it was during that speech that she most resembled the friend he still talks to every week.

"It felt very consistent with the people in her life," Taylor said.

From her lectures, Americans discovered that J.D. Vance learned how to cook Indian dishes that suited his wife's vegetarian diet, among other things.

She was also ready when the time came to defend her husband.

Last July, J.D. Vance's previous comments calling some Democratic politicians "childless cat ladies" resurfaced on social media, and his wife's damage control seemed best at quelling the ensuing uproar.

She described his remarks as a "quip," reframed them as reflections on the challenges facing America's working families and said she hoped critics would see what her husband said in a larger context.

She admitted in the Fox interview that she disagreed with her husband on all political issues, although she said she never doubted his intentions.

"Usha has never been an overly political person," JJ Snidow, the pair's former Yale Law School classmate, told the BBC. “Americans think of her as this impressive, introverted person, and that’s true — that’s who she is.”

Charles Taylor says Usha Vance doesn't fit into any political framework.

“A lot of people have trouble describing her political views, not because she’s secretive,” he said, “but because she doesn’t fit into the ideological tribe that most of us identify with.”

That may serve her well in her role as second lady of the United States, a role historically free from the entanglements of Washington's partisan politics.

But as J.D. Vance's star steadily rises, few people in the power couple suspect that Usha Vance will continue to serve as his spiritual mentor and may even one day become the First Lady of the United States.