Negative advertising works, but only when it strikes a chord with what voters already think

Negative election advertising has made an early debut on the big poster sites in the 2010 campaign. Do we think it's inevitable, desirable or potentially regrettable? All three, I'd say.

The Conservatives seem to have got the knocking stuff out there first with this weekend's beaming mugshots of Gordon Brown – always a scary sight – but the Observer's report that ministers plan to target George Osborne as the Tory "weakest link" suggests that Labour will not be far behind. Indeed, David Cameron's "lack of substance" will also be a recurring theme.

As things stand, Labour's new pledge card – five pledges on a sun-drenched background of a field of ripening corn was dismissed by the Guardian's creative designer, Mark Porter, as having "all the boldness of a muesli advert" in Saturday's edition.

Labour has made a virtue of sticking with its advertising agency, Saatchi & Saatchi, which is – as I'm sure you know – no longer owned by the Saatchi brothers, Charles and Maurice, who were behind Margaret Thatcher's lethal "Labour isn't working posters" in the 1979 campaign.

More interesting, as Patrick Wintour reports today, is the fact that ministers – and Saatchis – are trying to engage supporters in designing winning posters, some of which will go up on digital sites.

This is an attempt to adjust top-down messages to an interactive age. There's a lot of pent-up creativity out there, as the graffiti response to last month's airbrushed (?) Cameron/NHS poster demonstrated.

The Tories have been running soft ads for weeks, ones in which assorted voters – of all ages, shapes and colours – are seen saying things like: "I've never voted Tory, but I like their promise to … " improve health, education etc. I clocked several on the London-bound end of the M4/A4 yesterday.

But since their poll lead has shrunk in recent weeks, they generated headlines last week by rehiring what is now M&C Saatchi – ie Lord Maurice S and Mr Nigella Lawson – who are regarded as more aggressive.

I can't believe they have had time to dream up the new crop that you may have seen on 24/7 rolling news – the place where most "posters" are really meant to be seen nowadays. But the Daily Mail, which obligingly prints them all today, says they did.

The text that accompanies Brown's smiling face says things like "I caused record youth unemployment, vote for me", "I doubled the national debt, vote for me" and "I let 80,000 criminals out early, vote for me".

And so on. Actually, I inserted the commas there. The Saatchi text has no punctuation. "Vote for Dave and we'll get rid of punctuation" is therefore one legitimate response. But there are others that make this series a bit risky, I'd say.

Youth unemployment? Well, it's disappointingly high despite all the money pumped in. But was it better before 1997? National debt? Might Tory-voting bankers have had something to do with that? I think they might.

There's "I took billions from pensions vote for me", but, as we all know if we think about it, the real hit on pensions was not chancellor Brown's removal of generous tax arrangements – building on an earlier Tory Treasury policy, incidentally – it was the collapse of the stockmarket, the ending of final salary schemes (including mine) and other belated admissions that we couldn't afford what we thought we could when old people died so much younger.

People aren't stupid. They know these things. See how the recent "death tax" tombstone ad backfired. Everyone knows there's a problem with social care for the elderly that the winning party must address. "Death tax" talk is crude, as Cameron will find if he tries to tackle it – as he must.

As for Maurice and Charles's "I increased the gap between rich and poor vote for me" Brown poster, that is a jaw-dropping example of chutzpah that would probably be disbarred by the advertising standards authority.

The income/wealth gap in 1997 was dramatically wider than in 1979. Labour's efforts to close it have been conducted while running up a down escalator. The statistics are disputed, but valuable gains have been made at the bottom.

It's the escalating accumulation of wealth at the very top of the top that distorts the figures and much else. Yet the very newspapers that denounce Alistair Darling's "class warfare" efforts to claw some money back from the top 1% of earners or people buying £1m houses will also be the papers that parrot this allegation.

They already do. In today's Mail, my old chum Peter Oborne takes Labour's five pledges – the ones in the sunlit cornfield – and solemnly denounces them as "a mixture of pious aspiration, lies and outright fabrication. It is essential that they are exposed."

I'm sure it is and trust that other souls, equally zealous for the public good, will make a similarly selective analysis of Dave 'n' George's pledges. Me, I'll stick to chutzpah.

Meanwhile, my working hypothesis is that we all deplore negative advertising while being reluctant to admit, even to ourselves, that it often works. When does it work? When it strikes a chord with what voters already think and articulates half-felt impressions.

Thus the Tory "demon eyes" ad about Tony Blair in 1997, ridiculously camp I thought at the time, was laughed off in a way it might not have been in 2005. Whereas William Hague in a Thatcher wig (2001) was both witty and true – still is.

On the other hand, I have often written that Hague's "You paid the taxes, so where are the … " nurses, GPs, police officers, teachers etc poster was a very good one. It was just inappropriate in 2001 when voters were still giving Labour the benefit of the doubt and Billy himself was crying "save the pound" up and down Britain.

Will Cameron's attacks on Brown work? It's too early to say, as it is to be sure – as some people claim to be – that George Osborne, who faces Darling and Vince Cable in tonight's C4 debate – is the Tory weak link.

When Patrick Wintour and Nicholas Watt interviewed the PM for Saturday's Guardian – at dawn in Brussels for the EU summit – they found him much more cheerful and outgoing than they could recall.

Make of that what you will. Perhaps he knows that his fate will be decided – one way or the other – within the next month and is encouraged by the prospect of resolution, like a medieval knight facing single combat to resolve issues of courage and character which have dogged his life.

Either way, I'm still minded to say the Tories ought to win this election, negative posters or not, though they are doing their best to make it interesting – and to keep Gordon's spirits up.