In mid-December 2020, Robert Draper signed to write a book about the Republican party under Donald Trump, who spent four wild years in the White House but had just been beaten by Joe Biden.

“Trump hadn’t conceded,” Draper says, from Washington, where he writes for the New York Times. “But the expectation was that he would. The notion of the ‘Be there, will be wild’ January 6 insurrection had not yet taken root. And so I thought that the book would be about a factionalised Republican party, more or less in keeping with When the Tea Party Came to Town, the book I did about the class of 2010.”

“All that changed on my first day of reporting the job, which happened to be January 6, when I was inside the Capitol.”

The book became Weapons of Mass Delusion: When the Republican Party Lost Its Mind. It is a detailed account of Republican dynamics since 2020, but it opens with visceral reportage from the scene of what Draper calls the “seismic travesty” of the Capitol attack.

Draper says: “I still get chills, thinking about that day. It’s a Rashomon kind of experience, right? There were a lot of people in the Capitol and they all have different viewpoints that are equally valid.

“Mine was that of someone who just showed up figuring I would cover this routine ceremony of certification, ended up not being able to get into the press gallery, wandered around to the west side of the building and suddenly saw all of these police officers under siege, getting maced and beaten. After being there for a while, I escaped through the tunnels and went to the east side of the Capitol, and watched people push their way in.”

In their book The Steal, Mark Bowden and Matthew Teague observe that those who attacked the Capitol had no more chance of overturning the election than the hippies of 1967 had of seeing the Pentagon levitate. Draper’s term “seismic travesty” points in the same direction. But he does not diminish the enormity of the attempt, of Trump’s rejection of democracy and the threat posed by those who support him.

His book joins a flock on January 6. One point of difference is that each chapter starts with an image by the Canadian photographer Louie Palu, of January 6 and the days after it. Rioters surge. Politicians stalk the corridors of power.

Draper says: “There’s a reason why the subtitle isn’t how the Republican party lost its mind, but instead when the Republican party did. It is about a snapshot in time. I happen to think it is an incredibly momentous snapshot, but this is not a dry historical recitation of how the Republican party over decades moved from one mode of thought to another.”

“It’s important for me to impress upon readers that this is a discrete moment worth considering, a moment when the Republican party … rather than decide, ‘Wow, we’ve been co-conspirators, intended or not, to a horrific event, and we’ve got to do better,’ instead went in a different direction.

“And that to me is a moment when democracy is now shuttered and therefore has to be contemplated.”

Draper interviewed most major players, among them Kevin McCarthy, the House minority leader with his eye on the speaker’s gavel after next month’s midterms. Asked if the man who courted Trump with red and pink Starbursts and genuflections at Mar-a-Lago is the leader Republicans deserve, Draper answers carefully.

“So two operative words there are ‘leader’ and ‘deserves’. It depends on how you define either. He would be the leader in the sense of that they’ll probably vote for him for speaker … but it’s an open question as to whether he really will lead or whether he really has ever led.

“The important word is ‘deserves’. And obviously, that requires a judgment on my part. But I do think that what Kevin McCarthy embodies to me is the human refutation to the argument that Donald Trump hijacked the Republican party, because to imagine that metaphor, you imagine the Republican party as an airplane seized by force, without any complicity, and that the plane was a perfectly well-functioning plane before then. McCarthy is here to disprove all of that.

“McCarthy has been an absolute enabler of Donald Trump. He has never refuted the kinds of lies his party has embraced. He has winked and nodded along. People have told me that he’s offered to create for Marjorie Taylor Greene a new leadership position. At minimum, she’s likely to get plum committee assignments.”

Greene, a far-right, conspiracy-spouting congresswoman from Georgia, was elected as Draper began work.

“I thought she would be just kind of marginalised, sitting at the Star Wars bar of Republican politics, kind of a member of Congress who would be ousted after one term. But in a lot of ways, tracing her trajectory was a way of tracing the trajectory of the post– Trump presidency Republican party after January 6. Now, Trump is without question the dominant party leader, and more to the point, Trumpism is the straw that stirs the drink.”

Some in the media say Greene should not be covered. Some say strenuously otherwise. Draper spent time with her.

“This is the advantage of doing a book as opposed to daily journalism. It took me a year to get my first interview with her. You have to understand, to her, the mainstream media is, as Trump has delicately put it, the enemy of the American people. She thinks we habitually lie. We merit nothing but disgust, minimum, and contempt, maximum.

“And so to get her to kind of cross that psychological Rubicon and be willing to talk to me was a real process. But I do find in journalism and anthropology that people generally speaking want to let the rest of the world know why they are the way they are. They want to reveal themselves. And if you place them in a comfortable zone, where they feel like they can do that, and trust that they will not be made to pay for it immediately, then they often will, if only in increments, begin to reveal themselves. And that’s what happened with Greene and me.”

Democracy on the verge

Liz Cheney is in some ways Greene’s opposite. The daughter of Dick Cheney, vice-president under George W Bush, she is an establishment figure who broke from Trump only over the Capitol attack. Ejected from party leadership, she is one of two Republicans on the House January 6 committee but lost her seat in Wyoming to a Trump-backed challenger.

To Draper, it is “remarkable that we’re talking about those two female Republicans in the same breath, implicitly recognising these improbable opposite trajectories.

“In December 2020, if you and I were talking about Liz Cheney and saying, ‘What’s going to happen to her next,’ we wouldn’t say she’s going to be exiled from the party. And if we said, ‘What’s going to happen to Marjorie Taylor Greene next,’ we wouldn’t say she would basically be a more influential figure in the Republican party than Liz Cheney. It would seem a nutso proposition and yet that’s exactly what happened.

“Cheney stood almost alone in her view that not only did the party need to move on from Trump, but that it needed to see to it that Trump would no longer be a powerful force within the GOP. That put her on an island along with Adam Kinzinger and precious few others. She’s paid a heavy political price.”

Draper’s previous book, To Start a War, showed how Cheney’s father and his boss sold the Iraq war, citing weapons of mass destruction which did not exist. How did Cheney feel about that?

“She said, ‘You and I probably disagree on whether or not it was the right thing to do to go into Iraq.’ I remember saying to her, ‘You mean, I’m not a warmonger like you are?’ And she laughed, but she happens still to believe that was a viable proposition. And I think my book reaches the inexorable conclusion that [it] was a very foolish proposition.

“But it’s worth bringing that up, because … the subject at hand was not just Donald Trump, but also the Republican party and its tenuous grip on the truth. And it has been an eye-opener, I think, for a lot of us that Liz Cheney … stands for other things beyond ideology, and among them are the preservation of democracy.”

Before the Capitol was attacked, Cheney read Lincoln on the Verge, Ted Widmer’s account of Abraham Lincoln’s perilous rail journey to Washington in 1861.

Draper writes: “As the nation teetered on the brink of civil war, Lincoln avoided two assassination attempts on the journey, while the counting of electoral college votes in the Capitol was preceded by fears that someone might seize the mahogany box containing the ballots and thereby undo Abe Lincoln’s presidency before its inception.

“Cheney had shuddered to think what would have happened had the mob gotten their hands on the mahogany boxes on January 6, 2021.”

Widmer is a historian but plenty of books have suggested that with America deeply polarised and Trumpism rampant, we could be close to a second civil war. To Draper, “tragically it is not out of the question”.

“It’s certainly clear to me that when you’ve got a third of the voting public in America that believes that the election was stolen … [that’s] not something that you take with a grain of salt.

“America really is beset by fractures that could metastasize into something violent. I hope to hell that’s not the case. But but I’m not gonna look at you and say there’s no way it’ll happen.”

• Weapons of Mass Delusion: When the Republican Party Lost Its Mind is published in the US by Penguin Press