Since JD Vance got more political and decided to run for office, making sense of exactly the kind of politician he is and will be has been a challenge. There are different modes of Mr. Vance as a public figure. He has been the populist intellectual who works with Elizabeth Warren and also the tech podcast right-winger who talks about America as being in the “late republican period.” He can be the lawyerly professional on a Sunday show or the guy, when asked what makes him happy, who talks about anger.

Onstage as Mr. Trump’s vice-presidential nominee, he’s a blunt instrument, the attack dog going hard about illegal immigration and hammering Kamala Harris.

In his speaking over the past couple of years, and more recently, his emphasis has often been structural, ideological and hard-core. Visible in a lot of arguments from self-described national conservatives, the loose movement influential with the next wave of Republican politicians and academics, is a picture of America as fractured, declining and overcomplicated — that everything is so messed up in such a dense, decades-piled-up way that only a kind of big bang could fix it.

That vision is a hallmark of the Trump era but can become more academic and theoretical in the national conservative point of view. When Mr. Vance was asked in an interview about which historical figures he looks to for inspiration, he talked about post-World War II Charles de Gaulle.

Throughout much of the past decade of politics, you can find the idea of a society hopelessly in stasis and unable, because of ossified systems or financial interests, to deal with catastrophic changes that might ultimately threaten basic reality, like climate change and artificial intelligence. The national conservatives, like Mr. Vance, cite fertility and immigration as our existential problems.

Mr. Vance talks a lot about the decline in American manufacturing and the increase in trade over decades and the state of the border and the inflow of drugs into the United States today as growing out of financial incentives and the disregard that people in power had for the rest of the country. “We believe that a million cheap knockoff toasters aren’t worth the price of a single American manufacturing job,” he said in Nevada recently.

Mr. Vance’s intense, anti-immigration, structural approach can be even more apparent when he’s around ideological allies. “Look, the thing on immigration is that no one can avoid that it has made our societies poorer, less safe, less prosperous and less advanced,” he said at NatCon 4, the National Conservatism Conference, in July. He asked: “Why don’t our elites seem to care about it? Well, No. 1, they really benefit from the cheap labor. No. 2, they actually don’t really like the people who make up the domestic populations of their own country.”

This is the substance and edge that people detected in the old clips about childless leaders — the listener can feel Mr. Vance categorizing people into concepts and creating an ideological portrait of what he believes has gone wrong with America.

But he doesn’t always sound exactly like that.

At one of his first rallies as the vice-presidential pick, in Radford, Va., Mr. Vance was talking about a woman who spoke at the Republican convention about her son who’d died of a fentanyl overdose. He said he’d heard people say after the speech, well, maybe he shouldn’t have taken that pill to begin with. Mr. Vance then mentioned his own young children, listed their ages and said, “We all know kids make mistakes.” A few people in the crowd said, “Yes.” He added, to cheers, “I want them to grow up in a country where a simple childly mistake doesn’t cost our kids their lives.”

He had, darkly, called the boy’s death “the fruit of” Joe Biden’s border policy — a return to a structural point of view before discussing mistakes, which mapped less ideologically and less absolutely. It was a brief moment, but it contained just enough personalization and universality, and recognition of fallibility, that it briefly suggested a different kind of candidate.

When other politicians describe Mr. Vance, they talk about him more like that, in personal terms, about his life story and how it might connect with the voters and their ideas of themselves.

In Virginia, at one of Mr. Vance’s first solo rallies last month, for instance, one of the introductory speakers, Representative Morgan Griffith, combined Mr. Vance’s “humble beginnings” with those of two other speakers that day, one whose family had come from Vietnam as refugees and another whose mother had fled Cuba. The three had persevered, according to Mr. Griffith, evidence that the G.O.P. was becoming “the party of opportunity for everyone, not just those whose ancestors go back.” The Republican Party had claimed, Mr. Griffith said, “that mantle of the underdog fighting to be better, which America is proud of.”