Donald Trump named Sen. JD Vance of Ohio as his running mate on Monday, choosing a one-time critic who became a loyal ally and is now the first millennial to join a major-party ticket at a time of deep concern about the advanced age of America’s political leaders.“After lengthy deliberation and thought, and considering the tremendous talents of many others, I have decided that the person best suited to assume the position of Vice President of the United States is Senator J.D. Vance of the Great State of Ohio," Trump said in a post on his Truth Social network. The 39-year-old Vance rose to national fame with the 2016 publication of his memoir, “Hillbilly Elegy.” He was elected to the Senate in 2022 and has become one of the staunchest champions of the former president’s “Make America Great Again” agenda, particularly on trade, foreign policy and immigration.But he is largely untested in national politics and is joining the Trump ticket at an extraordinary moment. An attempted assassination of Trump at a rally Saturday has shaken the campaign, bringing new attention to the nation’s coarse political rhetoric and reinforcing the importance of those who are one heartbeat away from the presidency.Vance himself faced criticism in the wake of the shooting for a post on X that suggested President Joe Biden was to blame for the violence.“The central premise of the Biden campaign is that President Donald Trump is an authoritarian fascist who must be stopped at all costs,” Vance wrote. “That rhetoric led directly to President Trump’s attempted assassination.”Law enforcement has not yet specified a motivation for the shooting. Still, the pick is sure to energize Trump’s loyal base. Vance has become a fixture on the conservative media circuit and frequently spars with reporters on Capitol Hill, helping establish him as the kind of leader who could carry Trump’s mantle into the future, beginning with the next presidential election in 2028.But the pick also means that two white men will now lead the Republican ticket at a time when Trump has sought to make inroads with Black and Latino voters. In “Hillbilly Elegy,” Vance detailed life in Appalachian communities that drifted from a Democratic Party many residents found disconnected from their daily travails. While the book was a bestseller, it was also criticized for sometimes oversimplifying rural life and ignoring the role of racism in modern politics.Vance’s fame grew in tandem with Trump’s unlikely rise from a reality television star to Republican presidential nominee and eventually president. During the early stages of Trump’s political career, Vance cast him as “a total fraud,” “a moral disaster” and “America’s Hitler.”But like many Republicans who sought relevance in the Trump era, Vance eventually shifted his tone. He said he was proved wrong by Trump’s performance in office and evolved into one of his most steadfast defenders.“I didn’t think he was going to be a good president,” Vance recently told Fox News Channel. “He was a great president. And it’s one of the reasons why I’m working so hard to make sure he gets a second term.”Video below: JD Vance reacts to apparent assassination attempt on former president TrumpVance was rewarded for his turnaround during his bid for an open Senate seat in 2022, during which he landed Trump’s coveted endorsement and rode it to victory in a crowded Republican primary and a general election hard fought by Democrats. He is close to Trump’s son Donald Jr.Vance is now a Trump loyalist who has challenged the legitimacy of criminal prosecutions and civil verdicts against him and questions the results of the 2020 election.He told ABC News in February that, if he had been vice president on Jan. 6, 2021, he would have told states where Trump disputed Biden wins “that we needed to have multiple slates of electors, and I think the U.S. Congress should have fought over it from there.”“That is the legitimate way to deal with an election that a lot of folks, including me, think had a lot of problems in 2020,” he said.Many states adopted emergency measures four years ago to allow people to vote safely during the COVID-19 pandemic. But judges, election officials in both parties and Trump’s own attorney general have concluded there was no evidence of widespread voter fraud in the 2020 election.The relationship between Vance and Trump has been symbiotic.Vance’s book — subtitled “A Memoir of a Family and Culture in Crisis” — was embraced for its insights into Trump’s appeal in middle America, where manufacturing job losses and the opioid crisis had driven many families like his into poverty, abuse and addiction.The tale of Vance’s hardscrabble childhood in Middletown, Ohio, where he was born, and his familial eastern Kentucky hills region also captivated Hollywood. Ron Howard made it into a 2020 movie starring Amy Adams as Vance’s mother and Glenn Close as his beloved “Mamaw.”With his grandmother’s encouragement, Vance went on to serve in the Marine Corps, including in Iraq, and to graduate from Ohio State University and Yale Law School. From there, he joined a Silicon Valley investment firm before returning to Ohio to launch a nonprofit that he said would aim to develop opioid addiction treatments that might be “scaled nationally.”Ultimately, Our Ohio Renewal failed at that mission and was shuttered. During the 2022 campaign, then-U.S. Rep. Tim Ryan, his Democratic rival, charged that the charity was little more than a front for Vance’s political ambitions. Ryan pointed to reports that the organization made payments to a Vance political adviser and conducted public opinion polling, even as its actual efforts to address addiction largely floundered. Vance denied the characterization.As a senator, Vance has shown some willingness to work across the aisle. He and Ohio’s senior senator, Democrat Sherrod Brown, have teamed up on a number of issues important to the state, including fighting for funding for a $20 billion chip facility Intel is building in central Ohio and introducing rail safety legislation in response to the fiery derailment in East Palestine, Ohio.