You might not have heard of Rosanne Boyland. She made the 10-hour drive from Kennesaw, Georgia, to Washington on 5 January 2021. The next day, the 34-year-old died after losing consciousness in the crush of a mob of Donald Trump supporters as it surged against US Capitol police. She would never have been there, her sister said later, “if it weren’t for all the misinformation”.

The tragedy opens Barbara McQuade’s new book, Attack from Within: How Disinformation is Sabotaging America. The NBC News and MSNBC legal analyst explores how the deliberate spreading of lies disguised as truth has been weaponised to consolidate power in the hands of the few, undermine legal structures and drive voters such as Boyland. It is both cause and symptom of the US’s corrosive polarisation.

A former national security prosecutor, McQuade has seen the threat of disinformation evolve from al-Qaida to Islamic State to cyber-attacks from Russia. Teaching at the University of Michigan Law School, where she is a professor, she had her students study special counsel Robert Mueller’s report on 2016 election interference by Russia.

“I was fascinated by the details of accounts that were created by Russian operatives with names like Blacktivist or Heart of Texas posing as grassroots activists on the right or the left or various groups, and then taking very divisive stands on various issues just in an effort to sow discord,” McQuade, 59, says in an interview in the lobby of a Washington hotel.

It was then Trump’s bogus “stop the steal” movement in 2020, based on the big lie of widespread voter fraud rejected in more than 60 lawsuits and by his own attorney general, that inspired her to write the book. It considers lessons learned ahead of a potential repeat in 2024 as the US braces for a Joe Biden v Trump rematch.

“We will definitely get interference from foreign adversaries, including Russia and probably China, North Korea, maybe Iran, but there is a domestic part of this now where we are already hearing Donald Trump talk about how voting by mail is unreliable and laying the groundwork so that, if and when he loses, and there are more Democrats who have voted by mail than Republicans, he will have credibility.

“He will say: ‘See, I won the election and then it all flipped for me. It was fraud.’ The same strategy that he used in in 2020. I don’t know if he’ll have new strategies but ‘stop the steal’ was a classic disinformation influence campaign based on no evidence whatsoever.”

Trump commentary falls into categories. Some stop short of drawing comparisons with Adolf Hitler, perhaps wary of Godwin’s law, which holds that as an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches. Others dive in, arguing that some aspects of Trump’s authoritarianism, nativism and charisma do evoke the Nazi tyrant in enlightening ways.

McQuade goes there with an “authoritarian playbook” charting a brief history of disinformation from Hitler and Benito Mussolini to Jair Bolsonaro and Trump and noting the tactics: demonising the other, seducing with nostalgia, silencing critics, muzzling the media, condemning the courts and stoking violence.

She elaborates: “Hitler wrote in Mein Kampf that there are two things that are essential to effective propaganda. One was a very simple repeatable message because when people hear a message repeated again and again – and start hearing it from different sources – they begin to believe it to be true.

“The other is that the bigger the lie, the more likely it is to be believed. All of us are guilty of white lies from time to time that we might say out of kindness. My sister might say your hair looks fine when she means anything but, or my husband might say to me, no, dear, that dress doesn’t make you look fat.

“They’re saying these things out of kindness, even though they might be technically lying. As Hitler wrote in Mein Kampf, most people would not ever imagine that anyone could have the audacity to lie about something that is so significant – he was talking about the role of Jewish people in society, for example.

“But here the big lie for Trump was that the election has been stolen because people say: ‘How could you possibly pull that off? It’s so ridiculous.’ That’s part of what gives it its credibility and he knows that so I worry we’re going to begin to hear that again, and there are a significant number of Americans who still believe that the 2020 election was stolen. There will always be people who are manipulated by those strategies.”

Now the history of the January 6 insurrection itself is being rewritten, with the rioters recast as “patriots” and, if tried and imprisoned, as “hostages” whom Trump is promising to pardon if elected. Opinion polls show that more than a third of Americans believe that Biden’s election was illegitimate; Republicans are more sympathetic to the US Capitol rioters now than they were in 2021.

McQuade says with some dismay: “They assaulted people, they brought weapons, they broke windows, they spread faeces on the walls of the temple of democracy, they carried Confederate flags in there. Now to refer to it as legitimate political discourse or ordinary tourist activity, and then to refer to people who have been arrested, charged and imprisoned for their crimes as hostages, is absolutely a brand of disinformation. I’m curious to see how many people will continue to fall for that in this election.”

Trump svengali Steve Bannon, an arch election denier and vaccine conspiracy theorist, once memorably declared that the real opposition was the media and the way to deal with them was to “flood the zone with shit”. This brings to mind the Russian autocrat Vladimir Putin. McQuade cites the Russian author and journalist Peter Pomerantsev on “the fog of unknowability”.

She explains: “Everything is possible and nothing matters, and so everything’s PR because people begin to doubt the very existence of truth. One day Putin might say the missiles were shot by Ukraine; the next day the missiles were shot by Russia; the next day the missiles were shot by Nato.

“People don’t know what to think and consistency doesn’t matter. In fact, inconsistency is part of the point, because first people become angry and then they become cynical and then finally they become numb and disengaged from politics altogether and so that’s a very dangerous place for democracy.

“The other thing that people think in Russia is that truth is for suckers: you should just get what you can while you can and everybody is corrupt, which is one of the things that causes Donald Trump to constantly be suggesting that the Bidens are corrupt – if everybody is corrupt, then it gives you permission to overlook Donald Trump’s corruption, right?

“‘Well, they’re all corrupt. Who knows what to believe? All these investigations are themselves weaponised and corrupt so I might as well look for someone who is strong, who will advance my values despite all of his corruption.’ This normalisation of corruption is something that is part of it all as well.”

How has it come to this? McQuade, who was born in Detroit and lives in Ann Arbor, Michigan, identifies three central causes. First, the delivery mechanism of disinformation has changed. For centuries, the deceiver had to rely on word of mouth or leaflets or planting a false story, perhaps in a foreign newspaper, in the hope that someone would pick it up and pass it on. Now someone can spread a lie at the push of a button.

“Social media is a wonderful tool and can connect us to people all over the world in wonderful ways, but can also be used as a weapon when people want to and so it has been a really efficient vehicle for delivering disinformation,” says the author. “They’re completely unaccountable and we have ceded all of our power on social media to a handful of young bro billionaires, whose interest, of course, is in their own profits, not in the social good.”

Second, we are living through the worst political divisions in America since the 1861-1865 civil war. McQuade reckons it began with the combative, attention-grabbing Republican Newt Gingrich in the 1990s, and has grown as parties concentrate on turning out their bases rather than finding common ground. With elections framed as an existential struggle between good and evil, voters demand political purity. “If my tribe says X then I say X too, even if I don’t believe X to be true.”

Third, there is anxiety about a changing world: the climate crisis, refugees and border security, economic shifts with potential job losses. It is fertile soil for demagogues who promise that they alone can fix it. “We have leaders who want to use that to stoke fear because they perceive that that will be in their own political interest to attract those voters who are concerned about those changes and attract them into their own fold.

“It’s a combination of those three things that Donald Trump has exploited in this country like no one we’ve ever seen. I don’t think that he’s necessarily a political genius, but I do think he’s a conman and a marketing genius who knows how to sell things. He’s a huckster and he has taken advantage of this moment for personal and political gain.”

The huckster’s rise nearly a decade ago caught the media off guard. The old and laudable rules of balance, impartiality and not editorialising no longer seemed to work when one candidate was so blatantly mendacious. The New York Times newspaper broke the seal in 2016 with the headline: Trump Gives Up a Lie but Refuses to Repent. But as another election looms, McQuade worries that journalists have still not figured out how to cover him.

“That which is novel is always newsworthy, that which is controversial is always newsworthy, and so they present those things. But in an effort to present both sides of a story and in a tradition of not calling people liars, they have allowed Donald Trump and his supporters to manipulate them and play them. They’ll just say he made a statement that is not backed up by evidence; say he’s lying! You gotta say it out loud.”

But Attack from Within is not a letter of surrender or obituary of America. McQuade offers solutions for countering disinformation and maintaining the rule of law, such as making domestic terrorism a federal crime, reviving local journalism, criminalising doxxing (the act of revealing identifying information about someone online) and considering a ban on online anonymous accounts.

The former US attorney for the eastern district of Michigan urges politicians to get ahead of the curve of artificial intelligence. “I hope that our Congress can do something which we failed to do with social media, which is get ahead of it, because if it can put things in place before they create havoc, it’s much easier than trying to react after the fact.”

Individual citizens, she says, can gain skills be critical consumers of social media. “We can educate ourselves and take responsibility by doing things like, when we read an article, don’t rely just on the headline; we should actually read the article before we forward it to someone else.

“We should look for second sources of a story; if there’s an outrageous story, someone else will be reporting it. If there is data in a story, we should look at that data. How big was the sample set? Was it a sample of three or a sample of 3m? That makes a difference. Were the results of this study a causation or just coincidence with an outcome? We need to do that.”

McQuade also calls for increasing media literacy in schools and a revival of teaching civics rather than focusing on test scores. “Civics education is important for all of us, because when someone explains to you how the separation of powers works and how the three branches of government work, it is impossible to believe that a president could be immune from prosecution. We all need that education.”

• Attack from Within is out now