In his introduction to The American Experiment, his new book of interviews with historians and cultural leaders, David Rubenstein identifies 13 “genes” he says helped repel Donald Trump’s assault on US democracy. They range from access to the vote to the rule of law and freedom of speech and on to immigration, diversity and equality.

The billionaire co-founder of the Carlyle Group has made many donations to strengthen the bones of US democracy – giving millions for monuments to Washington, Jefferson and Lincoln and for founding manuscripts.

But access to the vote is under assault in many Republican states and those defending it could do with a boost. Is it time for Rubenstein to invest in a spot of genetic therapy?

He declines to be drawn.

“OK. It depends. Look, I get requests all the time. And I am announcing something soon relating to doing more for educating people about our country’s history.

“Voting rights is a more challenging thing, and finding the right organisation and so forth. I am obviously familiar with the issues, but I haven’t decided what to do with that area. I don’t know if I have enough money to make a difference there.”

Rubenstein has enough money – $4.3bn, according to Forbes – to make a difference most places. A huge opportunity came along in 2013, when he turned down a chance to buy a key part of the body politic, the Washington Post, and thereby protect one of his 13 key genes, freedom of speech. Amazon’s Jeff Bezos bought it instead.

“Jeff knows technology obviously better than I do,” Rubenstein says. “He has more resources. And the Post is in great shape today. I don’t think I could have done as good a job. So I regret it because I think it turned out to be a better deal than I thought it was. And I would have loved to own the Washington Post.

“I thought the interview with Don Graham [the publisher who sold the Post to Bezos] in The American Experiment was really good, because he talked about what it means to be a journalist and the responsibilities his family has. And I don’t know whether in England that would have been true of a publisher.”

Therein lies a feature of any interview with Rubenstein. He’s a prolific interviewer himself, not just at the Library of Congress and the New York Historical Society, for which many of the interviews in his new book were conducted, but on Bloomberg TV. Questions are often turned back on the questioner. In this instance, I mumble something like “Murdoch, maybe not” and we move on.

We have spoken twice before, for the first two books in Rubenstein’s series about American history and ideals. His subjects often open up. In the first interview, we discussed a revealing comment by former secretary of state Mike Pompeo who said Donald Trump saw foreign relations as a matter of economic leverage. A short time later, Trump was impeached for withholding military aid to Ukraine in search of political dirt.

In our second interview, Rubenstein discussed his own experience as an aide to a one-term president, Jimmy Carter. This time, we speak in the middle of the Kabul airlift, Joe Biden’s salvage mission amid the wreckage of America’s longest war, under heavy fire from opponents and the press. How does Rubenstein feel about comparisons of Biden and Carter, not least by Trump himself?

He points to both Biden’s astonishing political longevity and reassessments of Carter’s presidency.

“Remember, Biden was the first senator to endorse Carter [in 1976]. They had a very close relationship.

“Carter struggled throughout his presidency with lots of things that didn’t quite work out but we can go back in hindsight and look at all the things he did in four years. It’s dizzying when you think about it today. We’re happy if we can get one major bill through Congress in a year. And those days, we were getting bills left and right. And Carter, papers criticized him, said we’re getting too many things done. But he got a lot done.

“But for years he wasn’t able to project the image that he wanted, of strong leadership. And I think the inability to get the hostages out [of Iran] was fatal in his getting re-elected.”

Rubenstein has previously said much of Trump’s place in history would depend on his getting re-elected, so it was therefore too soon to judge. Whatever Trump says about electoral fraud – dangerous lies Rubenstein deplores on the page – he was not re-elected. Is Rubenstein willing to judge now?

He says he has read all the Trump books, including a deluge this summer, and clearly, “We can judge his presidency.” It’s clear from his book and our conversation that Rubenstein is appalled.

“But it’s not clear that that will be his only presidency. It’s not clear whether he’s going to run again or not … I don’t really think anybody who is close to Trump, and I wouldn’t say I’m close to him, really knows yet what he wants to do. I think he’s not going to say what he’s going to do until the last moment. That’s my guess.”

So far, so Zhou Enlai – the Chinese premier of the late 20th century who when asked about the impact of the French revolution, supposedly said it was too soon to tell.

The American revolution happened in 1776, 13 years before the French. To Rubenstein, it’s not too soon to tell readers a lot about that history. The American Experiment is another exuberant primer in history and civics, historians from Jill Lepore to Henry Louis Gates and cultural stars from Billie Jean King to Wynton Marsalis questioned by a man who reads widely and really knows his stuff.

I ask a question about a hypothetical: whether America missed a chance when it didn’t follow Thomas Jefferson’s train of thought about how the constitution might be revised every 20 years, so no generation could be held hostage by another.

“Well, I’ve also thought about this. When we had the constitutional convention, you had, you know, essentially all white, property-owning Christian men. What would a convention be like today, if we were going to have a new constitutional convention? Who would be the people there?

“Well, it obviously wouldn’t be all white men, or Christian, or property owners. It would be different, diverse, and what would they come up with? What would be different? Who would be the people, if you were to select 50 people to be in a constitutional convention?”

Chances are some of them would turn out to have been interviewed by Rubenstein, who mixes with the great and the good. In his new book the roster is notably more diverse – in answer, he confirms, to criticism of his first book. All consider challenges to his 13 key genes.

Trump’s lies about election fraud and the 6 January assault on the Capitol are there and if other existential threats – pandemic, the climate crisis, the rise of big tech, Black Lives Matter – are not directly addressed, that’s partly a matter of it being soon to tell and partly a matter of space. A conversation with John Barry, author of The Great Influenza, a seminal account of the pandemic of 1918, may appear in a future volume.

“There’s one thing you know for sure,” Rubenstein says. “If books sell you can probably do a sequel. If they don’t sell, there’s no interest in a sequel. So we’ll see how this one sells.

“The main point I really want to get across is that America is not a perfect country. No country is. We have the right principles, and we’ve been struggling to live up to them. And it’s been a struggle for a while.

“In the end, I dedicate the book to the public servants who made it possible for us to preserve our democracy [under attack from Trump]. I do think that, for example, had all the judges gone the wrong way, we’d be in a different situation today.

“I do think that we have a lot of great people who were determined to make sure we live up to these principles.”

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