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.