That a possible Trump prosecution is being discussed at all is a sign of the exceptional nature of the past four years. Those who argue in favor of legal action accept that there are powerful objections to going after Trump but urge people to think about the alternative – the dangers of inaction.

“If you do nothing you are saying that though the president of the United States is not above the law, in fact he is. And that would set a terrible precedent for the country and send a message to any future president that there is no effective check on their power,” said Andrew Weissmann, who was a lead prosecutor in the Mueller investigation looking into coordination between Russia and Trump’s 2016 campaign.

As head of one of the three main teams answering to the special counsel Robert Mueller, Weissmann had a ringside seat on what he calls Trump’s “lawless White House”. In his new book, Where Law Ends, he argues that the prevailing view of the 45th president is that “following the rules is optional and that breaking them comes at minimal, if not zero, cost”.

Weissmann told the Guardian that there would be a price to be paid if that attitude went unchallenged once Trump leaves office. “One of the things we learnt from this presidency was that our system of checks and balances is not as strong as we thought, and that would be exacerbated by not holding him to account.”