When JD Vance released his memoir “Hillbilly Elegy” in 2016, which charted an impoverished Rust Belt upbringing and rise through the Marines and Yale Law School, it caught the eye of Donald Trump. In it, the Iraq veteran describes his hometown’s worldview in the early 21st century.

“Nothing united us with the core fabric of American society,” he wrote. “We felt trapped in two seemingly unwinnable wars, in which a disproportionate share of the fighters came from our neighborhood, and in an economy that failed to deliver the most basic promise of the American Dream — a steady wage.”

Now, Vance is Trump’s running mate ahead of November’s election and the Republicans are polling well. Meanwhile, the U.S. is involved in two different wars, in Ukraine and the Gaza Strip (albeit with no boots on the ground), and anyone asking what the Ohio senator’s nomination means for America’s place in the world, if the GOP wins, might start in the communities of Vance’s youth.

“The guiding stars of his political alignment are economic populism, a degree of isolationism and a focus on the ‘forgotten man’ in U.S. politics,” said Clayton Allen, U.S. director at the political risk consultancy Eurasia Group.

Ideological lodestars like a rejection of free-market orthodoxy — once a central plank of the GOP economic policies — hostility toward immigration and most foreign entanglements, plus a healthy dose of social conservatism. Vance, embodying this combination, makes him the most visible advocate of a movement known as the New Right, currently ascendant in the Republican Party.

And ever since Trump rose to political prominence as a presidential candidate in 2016, he has appeared to relish challenging Washington’s long-held consensus on foreign policy, casting doubt on the value of U.S. alliances, trade deals and America’s far-flung military commitments. Now, Vance has “doubled down on Trump’s worldview, and put better, more coherent words to it,” said Bronwen Maddox, CEO of the London-based international affairs think tank Chatham House.

“He’s essentially 100% of Trump’s ideology but 50% the age, and that’s very much his appeal,” Allen said.

More than in any other foreign arena, Vance has sought to echo Trump on the Ukraine war.

He vocally opposed the $61 billion package of military aid for Ukraine that the Biden administration passed in April, and much like his senior partner, Vance has accused America’s NATO allies of not paying their fair share to support Kyiv. In doing so, he emphasized the thick vein of “scarcity politics” that runs through his foreign policy, arguing that the U.S. can’t equip Ukraine with enough materiel to hold back an opponent as vast as Russia.

Vance described Ukraine ceding territory to Vladimir Putin as being in “America’s best interest” while appearing more supportive than Trump of remaining in NATO.

Not so long ago, most older Republicans would have found it unthinkable for a fellow party member to make such comments. They represent “a big break from the old Atlanticist view that the U.S. is there in lockstep with Europe to underpin a certain set of values and the security of the countries that represent those values,” Chatham House’s Maddox said.

She also suggested that view might come from Vance’s own military experience and the risking of American lives and money in places that don’t seem to appreciate it. As such, Vance is a product of his time.

While he touts the lessons of military service in “Hillbilly Elegy,” he has more recently raised hawkish eyebrows with his speech at this month’s Republican National Convention that attacked President Joe Biden for voting in favor of the Iraq War when he was a senator.

Vance sought to link the last three decades of policies to an “establishment” exemplified by Biden, a Democrat, even though the policies he skewered the president for were broadly supported by Republicans.

“When I was in the fourth grade, a career politician by the name of Joe Biden supported NAFTA, a bad trade deal that sent countless good jobs to Mexico,” Vance also said during the RNC on July 17. “When I was a sophomore in high school, that same career politician named Joe Biden gave China a sweetheart trade deal that destroyed even more good American middle-class manufacturing jobs.”

“When I was a senior in high school, that same Joe Biden supported the disastrous invasion of Iraq, and at each step of the way, in small towns like mine, in Ohio, or next door in Pennsylvania and Michigan, in other states across our country, jobs were sent overseas, and our children were sent to war,” he added.

Vance’s isolationism doesn’t just send a message about a potential second Trump administration: His selection shows that, in the Republican Party at large, a genuine debate is underway on foreign affairs issues that for decades were taken as read, said William Ruger, president of the American Institute for Economic Research, a think tank based in Great Barrington, Massachusetts.

But observers disagree as to whether Vance, who many say will sharpen Trump’s sometimes jumbled foreign policy, represents a new vision or merely a collection of ad hoc positions — he wants to cede Ukrainian territory, send troops into Mexico to fight cartels and unconditionally arm Israel — that reflect the former president’s transactional approach to international affairs.

That question looms over the ticket’s fondness for a broad array of strongmen — Trump has embraced Brazil’s Jair Bolsonaro and Vance is fond of Hungary’s nationalist and Kremlin-friendly Viktor Orban. It also underscores the bind Vance might find himself in over his boss’s pronouncements on Taiwan.

While Vance told Bloomberg this month that “the thing that we need to prevent more than anything is a Chinese invasion,” Trump complained to the same publication in the same week about Taipei’s industrial successes and the cost of protecting the island.

“They did take about 100% of our chip business. I think Taiwan should pay us for defense. … Taiwan doesn’t give us anything,” Trump said.

That mismatch hints at two elements of the Trump-Vance relationship.

The first: Though Vance “may be the most influential vice president since [Dick] Cheney” in George W. Bush’s administration, he will have to let Trump be Trump, Allen, of the Eurasia Group, said. That may not be a problem, as the two share a broad ideology rather than fixed policies, he added.

The second: The man who once compared Trump to Hitler is “a bit of a careerist,” Allen said. “He recognizes that alignment with Trump is the fastest way to the top.”

That’s not something Vance’s predecessor, Mike Pence, valued — a calculation that almost had dire consequences.

The foreign policy views of Pence, vice president when Trump was in office, while not loved by everyone, were at least “mature” — they were informed by several terms experiencing the consequences of foreign policy becoming reality, according to Daniel Kurtzer, a former U.S. ambassador to Israel and now a professor at Princeton. Vance, on the other hand, brings “no foreign policy experience, certainly no expertise,” Kurtzer says, and he will fall in behind his boss when needed.

China is less likely to be a source of disagreement.

Globalization driven by a booming Chinese economy drove the postindustrial blight that Vance describes in his memoir. Besides, tariffs against China and a deep distrust of Beijing’s international intentions enjoy broad bipartisan support. Experts expect Trump to keep and maybe expand levies and increase pressure on China over its global ambitions.

Also like Trump, Vance has called for an immediate end to the war in Gaza, but rather than that being down to concerns about the Palestinian civilian death toll or shifting support for the government of Prime Minister Benjamin Netanyahu, the stance is economically motivated, according to Charles Hollis, a former U.K. diplomat in Saudi Arabia and Iran.

Trump’s “not really a warmonger,” explained Hollis, who is head of strategic intelligence at Aperio Intelligence. “He seems to think that doing business is what it’s all about and wars disrupt that.”

Vance may have even a more hard-line take on the war in Gaza, Hollis said, pointing out that he was one of the few senators who tried to strip out aid for Gaza from a broader Middle East support bill in April. If he gets into office, Vance, who “has never really had to think very hard about Israel,” may “find the need for more nuance” in his black-and-white view of the region, Hollis said.

That combination of Trump’s mercurial but hard-line foreign policy with Vance’s outlook, which Princeton’s Kurtzer characterizes as viewing the world entirely through the prism of America’s borders and interests, may scare off potential U.S. allies.

Right now, it’s unlikely that a Trump-Vance administration would reintroduce tariffs on Canada and Mexico, but the lessons of Trump’s first term will linger long in the memory of America’s allies. “You get countries around the world saying, ‘My goodness, if that’s how the U.S. treats its friends, how’s it going to treat others?’” said Chatham House’s Maddox.

That nagging questions may have a real impact, especially in Europe, Maddox added: “Europe [may start] dealing more with China [and] taking a different tone towards Israel,” she added.

It’s a disruptive scenario that may be unfamiliar to Vance, with his year and a half as a Midwestern junior senator. But it won’t be to Trump, who could become the first U.S. president to serve two nonconsecutive terms since Grover Cleveland at the end of the 19th century. If he does, former diplomats and analysts say that Vance — disjointed and hard-line worldview or not — will ultimately follow his master’s voice.