Is the Tory election guru, Lynton Crosby, a double agent? And if not, why is he trying so hard to lose this unloseable election? Exaggerated assaults on personalities famously don’t work in elections, because we all get to see the candidates on TV and judge them for ourselves. You would have thought Crosby might have learned from his failed attempt to portray Sadiq Khan as an associate of extremists in last year’s London mayoral election. The mild-mannered Khan doesn’t come across as anything like an extremist, and never did.

The 1992 Tory 'tax bombshell' campaign sank John Smith’s shadow budget by pointing out that it would cost people

In the early 1980s Margaret Thatcher and much of the press heaped abuse on the newly elected leader of the Greater London Council, Ken Livingstone, as an associate of the IRA and general bad boy. But Livingstone appeared on TV sofas and came across as a south London cheeky boy who made you laugh (this is a long time ago), not a hard man of violence. The public might have thought less of him if they weren’t judging him against the stark messages that preceded his public appearances.

Outside a major election, or the highest elected offices, the media can shape personal reputations to a considerable degree. But when the public have direct access to the people concerned, attempts to mould the public’s view can be counterproductive when it turns out that in comparison to the scaremongering, whoever it is being demonised is not so bad after all.

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Another obvious mistake from the past that the Tories are ignoring is their melodramatic effort to portray Tony Blair, with demon eyes, as a red hot socialist in the run-up to the 1997 election (left). The public’s not daft, Blair was obviously a moderate centrist and rather polite to boot, and all that campaign did was damage the credibility of the source (it may also have helped Blair shake off any danger of having a feeble, Bambi image).

Contradicting what people see and hear for themselves can be very damaging to your credibility. An example of this outside politics is the hard-hitting TV advertising campaign run by the government in the early stages of the Aids epidemic in the 1980s. It was highly effective in scaring people, with images of tombstones and icebergs and the strap line “Don’t die of ignorance”.

The strapline is remembered to this day, but the campaign was a disaster. Viewers went to the pub as usual, looked around and saw no one looking near death, and so ignored not just these warnings but all future communications from the government on the subject of Aids.

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Political criticism, at least in the UK, needs to be credible and based on facts – and facts matter to the electorate. The 1992 Tory “tax bombshell” campaign sank John Smith’s otherwise appealing shadow budget by pointing out that it would, of course, cost people. The same can be said of the Labour refrain during the 1997 election campaign – that John Major had raised taxes 24 times, having promised not to raise them at all. Of course, Major had no choice after black Wednesday and the UK’s undignified exit from the exchange rate mechanism, but many who voted Tory had believed his promise and thought the whole point of the Conservative party was to reduce taxes. People were feeling poorer and Labour had named the culprit, and they were furious.

But this is a very different matter from the current refrain of “yah boo, Corbyn is a terrorist”. If the Conservatives feel the need to attack the Labour leader personally, it would be more apposite to direct their attack against what is both real and obvious in the TV interviews: he is a dreamer who would like world peace and an end to poverty but hasn’t a clue how to achieve either. Nice, but out of his depth. That would fit much better.