Vance, 40, has spoken of Trump, 78, as a kind of father figure, albeit one who can call multiple times in a day and at any hour.

Some of those calls from Trump were check-ins and encouragement during the onslaught of criticism over Vance’s complaints of too many “childless cat ladies” among American leaders, including Harris. Trump urged Vance to hold his ground and fight through the attacks. Democrats have seized on Vance’s socially conservative views to paint the Republican ticket as weirdly out of touch, while Trump and his team view him as an ideal messenger to motivate the working-class base of voters they need to win.

Vance has spoken publicly about another call in which Trump heard him trying to quiet his seven-year-old son, Ewan, and asked to speak with the boy. When Vance put his eldest child on the phone, Trump asked the youngster for feedback on a campaign statement he was preparing.

Vance has also hinted, albeit jokingly, at what would be an understandable fear of Trump’s demanding style and hair-trigger wrath, while recounting how he initially missed the call when he phoned to offer him the vice president slot.

“I call him back, he answers the phone and says, ‘JD, you missed a very important phone call and now I might have to pick somebody else’,” Vance recalled last week in North Carolina. “So I almost have a heart attack right there.”

The Trump-Vance partnership remains, undoubtedly, a fledgling one. The two men first met only a few years ago, when Vance commenced a political career and needed to make amends for his venomous past as a Never Trumper.

Long-term security is more of a bug than a feature in any Trump relationship. The former president has treated his closest family and friends mercurially and has a history of dispassionately abandoning longtime allies — including his previous running mate, former vice president Mike Pence — when it suits his political purpose.

Lee Zeldin, a Republican and former congressman from New York who is close with both men, said Trump easily jelled with his running mate thanks in part to personal testimonials from family and longtime advisers who attested to Vance’s political conversion and reliability.

Their trust quickly deepened, Zeldin said, over a mutual affection for economic populism, staunch anti-immigration policy and a restrained approach to international affairs – plus a similar instinct for the jugular on the campaign trail.

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“They’re friends, and they have a very strong relationship,” Zeldin said. “They’re more like buddies or confidants who can be frank with each other and enjoy the time they spend together.”

But while Trump has not publicly crowned Vance as the heir apparent to his red-capped conservative movement, he has never stopped his campaign from describing his running mate that way since joining the ticket two months ago.

”Senator Vance reinforces President Trump’s worldview and shows there is a strong carrier of this movement to fight for American workers and take away the power from the entrenched elites,” said Jason Miller, a senior adviser for the Trump campaign. Trump also has a deep respect for Vance’s willingness to fight for the ticket on television, Miller added.

Trump has let Vance freelance in ways he has rarely entrusted to other allies. The two men talk frequently, but Vance does not check each decision with Trump – the former president values that as a sign that Vance has confidence and that he’s not “needy and high maintenance,” according to one Trump aide.

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But the latitude Trump has afforded his running mate has led to some potentially uncomfortable moments, most recently over the Vance-led offensive against Haitian migrants as pet-eating monsters.

The attacks drove headlines for days and threatened to make a Trump campaign that has promised to prioritise mass deportations from the White House appear even more radical and extreme. The Haitian migrants who suddenly found themselves the target of baseless claims that they were eating their neighbours’ pets are not an example of illegal border crossings. They are lawfully living in the United States with temporary protected status, a federal designation to protect people from a country in crisis.

But Trump was never remotely upset. Instead, he joined in. In front of a televised audience of 67 million people who tuned in for his debate with Harris, he pushed the attacks even further.

“They’re eating the dogs, the people that came in — they’re eating the cats, they’re eating the pets of the people that live there,” Trump said.

After the debate, Vance left the media filing centre in Philadelphia and inadvertently encountered Trump. Standing amid lighting fixtures and boxes of unused equipment stacked on the back side of a blue curtain, the two men briefly huddled, as if they were a pair of everyday buddies.

Trump noted that he was going to talk to reporters. Awesome, Vance told him, adding that he was heading to a cable news interview. Awesome, Trump responded. They compared notes on the debate and incoming questions from the media. When they parted ways, Trump gave his running mate an encouraging pat on the shoulder.

“Go get ’em,” Trump told Vance.

This article originally appeared in The New York Times.