The US presidential election is neck and neck. But only one candidate has been compared to Adolf Hitler. Is it an exaggeration or based in fact?

Is Donald Trump really a fascist? It’s a question that has been bubbling away since he first announced his candidacy for the Republican presidential nomination in 2015 after a years-long campaign to brand Barack Obama an illegitimate occupant of the White House. Back then his questioning of Obama’s citizenship appeared overtly racist (“When I was 18, people called me Donald Trump. When he was 18 @BarackObama was Barry Soweto”). So were his comments about Mexican immigrants at his campaign launch: “They’re bringing crime. They’re rapists. And some, I assume, are good people.” Trump’s early indications that he would not accept the results of any election he did not win made him sound like an anti-democrat. And he told Hillary Clinton in their first presidential debate that if he became president, she would end up in jail, which is where he seemed to think his political opponents belonged. It was plenty. But was it fascism?

Before 2016, the closest the US had ever come to electing a fascist as president was in a work of fiction. Philip Roth’s The Plot Against America, published in 2004, imagines an alternative history for the country in which Charles Lindbergh – real-life aviation hero and Nazi sympathiser – has defeated Franklin Roosevelt in the 1940 presidential election on a promise to keep the US out of the second world war. In Roth’s telling, Lindbergh then initiates non-aggression pacts with Hitler’s Germany and Imperial Japan before embarking on a domestic programme of forced Jewish assimilation. Only when the popular radio host Walter Winchell announces he will stand against Lindbergh for the presidency and is shot dead at a campaign rally does the country come to its senses and drive Lindbergh out.