Introducing himself to the nation after being tapped as Donald Trump’s running mate, JD Vance used his Wednesday night address to the Republican National Convention to share the story of his hardscrabble upbringing and make the case that his party best understands the challenges facing struggling Americans.

The 39-year-old Ohio senator is a relative political unknown, having served in the Senate for less than two years. In his first prime-time address since Trump made his pick, Vance cast himself as fighter for a forgotten working class, making a direct appeal to the Rust Belt voters who helped drive Trump’s surprise 2016 victory and voicing their anger and frustration.

“In small towns like mine in Ohio, or next door in Pennsylvania, or in Michigan, in states all across our country, jobs were sent overseas and children were sent to war,” he said.

“To the people of Middletown, Ohio, and all the forgotten communities in Michigan, Wisconsin, Pennsylvania and Ohio, and every corner of our nation, I promise you this,” he said. “I will be a vice president who never forgets where he came from.”

Vance, who rapidly morphed in recent years from a bitter critic of the former president to an aggressive defender, is positioned to become the future leader of the party and the torch-bearer of Trump’s “Make America Great Again” political movement, which has reshaped the Republican Party and broken longtime political norms. The first millennial to join the top of a major party ticket, he enters the race as questions about the age of the men at the top — 78-year-old Trump and 81-year-old Biden — have been high on the list of voters’ concerns.

At his first fundraiser as Trump’s running mate earlier Wednesday, Vance was introduced by Indiana Rep. Jim Banks, who said Trump’s decision to choose him wasn’t about picking a running mate or the next vice president.

“Donald Trump’s decision this week in picking JD Vance was about the future,” he said. “Donald Trump picked a man in JD Vance that is the future of the country, the future of the Republican Party, the future of the America First movement.”

In his prime-time speech, Vance shared his story of growing up poor in Kentucky and Ohio, his mother addicted to drugs and his father absent. He later joined the Marines, graduated from Yale Law School, and went on to the highest levels of U.S. politics — an embodiment of an American dream he said is in now in short supply.

“Never in my wildest imagination could I have believed that I’d be standing here tonight,” he said.

The first millennial on a major-party ticket, Vance spent much of his speech talking up Trump and going after Biden, using his relative youth to draw a contrast with the 81-year-old president.

“Joe Biden has been a politician in Washington as long as I’ve been alive,” Vance said. “For half a century he’s been a champion of every single policy initiative to make America weaker and poorer.”

The crowd inside the convention hall welcomed Vance warmly. They erupted into chants of “Mamaw!” in honor of his grandmother, and chanted “JD’s Mom!” after he introduced his mother, a former addict who has been sober for 10 years.

Vance was introduced Wednesday night by his wife, Usha Chilukuri Vance, who talked of the stark difference between how she and her husband grew up — she a middle-class immigrant from San Diego, and he from a low-income Appalachian family. She called him “a meat and potatoes kind of guy” who became a vegetarian and learned to cook Indian food for her mother.

Along with his relative youth, Vance is new to some of the hallmarks of Republican presidential politics: This year’s gathering is the first RNC that Vance has attended, according to a Trump campaign official who was not authorized to speak publicly.

Trump, who entered the arena to a version of the song “It’s a Man’s World” by James Brown and Luciano Pavarotti, will be watching from his family box.

Convention organizers had stressed a theme of unity, even before Trump survived an attempted assassination at a rally in Pennsylvania Saturday. Trump’s refusal to accept the results of the 2020 election and the subsequent attack on the U.S. Capitol, officials said, would be absent from the stage.

But that changed with former White House official Peter Navarro, who was greeted with enthusiastic cheers and a standing ovation hours after he was released from a Miami prison where he served four months for defying a subpoena from the congressional committee investigating the Jan. 6, 2021, attack on the U.S. Capitol by a mob of the former president’s supporter.

“If they can come for me, if they can come for Donald Trump, be careful. They will come for you,” he said in a fiery speech. He compared his legal troubles to those faced by Trump, who earlier this year was convicted on 34 felony charges in his criminal hush money trial. Trump is also facing two indictments for his efforts to overturn the 2020 election.

“They did not break me,” Navarro said, “and they will never break Donald Trump.”

Also spotted on the floor of the convention: Paul Manafort, Trump’s 2016 campaign chair, who was convicted as part of the investigation into Russia’s meddling in that election.

Vance is an Ivy League graduate and former businessman, but gained prominence following the publication of his bestselling 2016 memoir “Hillbilly Elegy,” which tells the story of his blue-collar roots. The book became a must-read for those seeking to understand the cultural forces that propelled Trump to the White House that year.

Still, most Americans — and Republicans — don’t know much about Vance. According to a new poll from the AP-NORC Center for Public Affairs Research, which was conducted before Trump selected the freshman senator as his choice, 6 in 10 Americans don’t know enough about him to have formed an opinion.

About 2 in 10 U.S. adults have a favorable view of him, and 22% view him negatively. Among Republicans, 61% don’t know enough to have an opinion of Vance. About one-quarter have a positive view of him, and roughly 1 in 10 have a negative one.

Trump’s eldest son, Donald Trump Jr., who is a close friend of Vance, also had a prime-time slot and talked about the unlikely friendship between “a kid from Appalachia and a kid from Trump Tower in Manhattan.”

“JD Vance is going to make one hell of a vice president,” he said.

He also turned the microphone over to his daughter, Kai, who delivered a humanizing speech, calling her grandfather “just a normal grandpa” who calls her while she’s at school to talk about golf.

“The media makes my grandpa seem like a different person but I know him for who he is,” she said.

Kai Trump spoke about the shock of learning her grandfather had been shot.

“I just wanted to know if he was okay,” she said. “It was heartbreaking that someone would do that to another person.”

Beyond Vance’s prime-time speech, the Republican Party focused Wednesday on a theme of American global strength.

In a particularly powerful moment, the relatives of service members killed during Biden’s disastrous withdrawal from Afghanistan took the stage, holding photographs of their loved ones.

Christy Shamblin, whose daughter-in-law Marine Sgt. Nicole Gee died in the attack, spoke of the six hours she said Trump spent with her family in Bedminster, New Jersey.

“He allowed us to grieve. He allowed us to remember our heroes,” she said, adding that Trump “knew all of our children’s names” and “spoke to us in a way that made us feel understood.”

“Donald Trump carried the weight for a few hours with me. And for the first time since Nicole’s death I felt I wasn’t alone in my grief,” she said.

Herman Lopez, whose son, Marine Cpl. Hunter Lopez, was among those killed, read aloud the names of all 13 U.S. service members who died in the Aug. 26, 2021, attack.

His wife, Alicia, said they have another son in the Army. “We do not trust Joe Biden with his life,” she said. The families have blasted Biden for never publicly naming their loved ones.

Also featured were the parents of Omer Neutra, one of eight Americans still being held hostage in Gaza after the Oct. 7 attack by Hamas.

His parents, Ronen and Orna, said Trump called them after their son, a soldier in the Israeli army, was captured, and offered support. As they spoke, the crowd chanted “Bring them home!” Many waved Israeli flags.

Republicans contend that the country has become a “global laughingstock” under Biden’s watch. The party that was once home to defense hawks and neoconservatives has fully embraced Trump’s “America First” foreign policy that redefined relationships with allies and adversaries.

Democrats have sharply criticized Trump — and Vance — for their positions, including their questioning of U.S. support for Ukraine in its defense against Russia’s invasion.

In a video released Wednesday by Biden’s reelection campaign, Vice President Kamala Harris dismissed Vance as someone Trump “knew would be a rubber stamp for his extreme agenda.”

“Make no mistake: JD Vance will be loyal only to Trump, not to our country,” Harris says in a video.