We now know how Donald Trump will take on Hillary Clinton this autumn – by framing her as a criminal who should be sent not to the White House, but to jail.

Trump had already signalled as much via the two-word label he likes to hang around the neck of his Democratic opponent: Crooked Hillary. But the Republican convention in Cleveland, which on Tuesday formally nominated Trump as its presidential candidate, has given colour and shape to that strategy. Now we know how it will look and sound.

Speaker after speaker has pressed the same themes: that Clinton is a liar who regards herself as above the law, that she is corrupt, that she is stained by a series of scandals going back 25 years. On Tuesday night, New Jersey governor Chris Christie used his turn at the podium to play prosecutor, asking the audience in the hall and watching on TV to act as a “jury of her peers” and sit in judgment on Hillary Clinton as he laid out the case against her.

Paul Owen (@PaulTOwen) Republican crowd chants "lock her up" about Hillary Clinton. Chris Christie: "All right, we're getting there" https://t.co/A7BCEidbl0

He had barely got going when the crowd in front of him began chanting “Lock her up! Lock her up!” Christie smiled indulgently, before promising: “All right, we’re getting there.”

It was a telling moment, for it confirmed that, when it comes to this line of attack, the Republican party and the Trump campaign are following as much as they are leading. The activists of the right have been banging this same drum for months; some of them have been doing it for years. On Monday, in a lakeside Cleveland park, a rally convened by longtime Trump backer Roger Stone and the conspiracy theorist Alex Jones was peppered with posters urging “Hillary for Prison”, alongside placards depicting the Democratic candidate as “wanted”, in the style of the old west. Also spotted around town: pictures of Clinton in an orange jumpsuit and behind bars.

Jonathan Freedland (@Freedland) And a poster on a Cleveland street corner as the city prepares for the anointing of Donald Trump #RNC2016 pic.twitter.com/4cs4OD5OmO

Christie sought to give substance to those slogans and memes. Much of his case related to policy decisions Hillary Clinton had taken, especially as secretary of state. But now those decisions – to negotiate a nuclear deal with Iran or to thaw relations with Cuba – were refashioned as crimes. And as he worked through each item – Libya, Syria, China – he invited delegates to bellow their verdict. Never mind that some of the accusations were bizarre – including the claim that Clinton was an “apologist” for Boko Haram – the hall answered loudly and in chorus: “Guilty!”

The old favourites got a run-out too, naturally. Hillary, said Christie – who having been passed over as a vice-presidential choice hopes to be attorney general in a Trump administration – had lied about the deaths of four US diplomats in Benghazi, deaths for which, according to earlier speakers in Cleveland, Clinton was directly culpable. And she had lied about her use of a private email server, offering an account which, Christie reminded his audience, the director of the FBI had recently deemed untrue.

The audience lapped it up, of course they did. For this is the one thing on which all Republicans, those who backed Trump and those who opposed him, can agree: that Hillary Clinton is so corrupt that she must not be allowed to become president. Indeed, my conversations with delegates previously hostile to Trump suggest that this is what enables them to fall in behind the nominee: their belief that, morally speaking, Clinton is even worse.

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Strategically, you can see Team Trump’s logic. The polls are staggeringly bad for Clinton on this, with some 67% of Americans regarding her as not honest or trustworthy. It makes sense for Republicans to exploit that weakness.

But there is a larger calculation at work. The Trump campaign has clearly concluded that there is not much it can do about their man’s stratospherically high disapproval ratings. (He is regarded as dishonest by 62% of Americans, for example, and his other numbers are even worse.) So if they can’t lift him up, they might as well tear her down.

The result will be a relentlessly negative campaign from now until November, with both candidates depicting the other as the greater evil. And if talk of evil, rather than the merely criminal, sounds excessive, consider Tuesday’s closing speech by one of Trump’s former fellow candidates, Ben Carson. He suggested Clinton was a devotee of a man, the long-ago radical Saul Alinsky, who had once praised … Lucifer. Yes: Hillary Clinton was just one degree of separation away from Satan. If this is what the Republicans are saying about their Democratic opponent in July, imagine what they’ll be saying come November.