Milwaukee, Wisconsin - Donald Trump's vice presidential pick JD Vance sought to light up the Republican National Convention Wednesday with a speech leaning heavily on his personal story as he tried to connect his turbulent upbringing with the hardships faced by millions of Americans.

In his first formal address since being tapped as Trump's running mate on Monday, Vance offered his account of growing up poor, with no father at home and a mother hooked on drugs.

"I grew up in Middletown, Ohio – a small town where people spoke their minds, built with their hands and loved their God, their family, their community and their country with their whole hearts," he said.

"But it was also a place that had been cast aside and forgotten by America's ruling class in Washington."

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The story will be familiar to readers of his best-selling memoir Hillbilly Elegy, an account of his Appalachian family and modest beginnings that gave a voice to rural, working-class resentment in left-behind America.

But it was his first real introduction to many tuning in at home, and the Trump campaign is banking on the address chiming with blue-collar voters in the swing states key to winning November's election rematch against President Joe Biden.

Vance emphasized his background as a former US Marine, making him the first veteran on a major party ticket since Republican John McCain ran for president in 2008, and talked about meeting his wife Usha at law school.

Vance touched on trade, foreign policy, and the drug epidemic – and on Trump's policies for addressing them – but he devoted much of the speech to his own experiences, bringing his mom, who has been sober for a decade, on stage afterwards.

Slamming Biden's presidency, he called for a leader "not in the pocket of big business (who) answers to the working man – union and non-union alike."

"There is still so much talent and grit in the American heartland, there really is. But for these places to thrive, my friends, we need a leader who fights for the people who built this country," he said.

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The one-term senator, who will be just 40 on inauguration day, would be the third-youngest vice president in history – and one of the least experienced – if 78-year-old Trump defeats Biden.

Even before his big moment, Vance was a hit with the party faithful in Milwaukee's Fiserv Forum arena. They rewarded him with boisterous applause as he arrived with his wife on the opening day Monday to take his place with the Trump family in the front row.

While Vance reinforces Trump's appeal to the hardline base, he offers little chance of broadening the tent to more moderate voters and women.

He is further to the right than Trump on some issues including abortion, where he embraces calls for restrictive federal legislation.

Some 50,000 Republicans have descended on the shores of Lake Michigan for the four-day convention, which came with the country reeling from a gunman's failed assassination attempt on Trump at a rally in Pennsylvania on Saturday.

The attack – which killed one bystander and left the ex-president with a bloodied ear – has dominated proceedings.

Trump's daily convention appearances, complete with bandage over the wound, have been a highlight and Vance praised Trump's reaction to the attack at length as he opened his address.

"What did he call us to do for our country? To fight for America," Vance said.

"Even in his most perilous moment we were on his mind, his instinct was for us, for our country, to call us to something higher, to something greater."

Once a harsh critic, Vance has since grown into cheerleader-in-chief for Trump's foreign policy – notably including opposition to further US support for Ukraine in its war with Russia – and populist defense of the ordinary worker.

"Wall Street barons crashed the economy and American builders went out of business... We're done, ladies and gentleman, catering to Wall Street. We'll commit to the working man," he said.

He urged voters to "choose a new path" as he accepted his nomination, telling the crowd: "The people who govern this country have failed and failed again."