A poll lead as small as two percentage points, hostile mutterings from the cheap seats, and only weeks until the general election – what has been happening to the Tories? Explanations for their recent wobble have included the fuzziness of Conservative policy, the public's queasiness about a looming age of austerity, and much more besides, but at least part of the story is traceable to an unassuming 41-year-old called Clifford Singer, and one of the most inspired acts of online mischief British politics has yet seen.

On 5 January, the Tories launched their first big move of the campaign. At a cost of around £500,000, they hired 759 billboard sites across the country, and plastered them with a now-infamous image of David Cameron and the words, "We can't go on like this. I'll cut the deficit, not the NHS." At first, coverage focused on the apparent airbrushing of Cameron's features (denied in his recent interview with Trevor McDonald), and the clear echo of prime-period Tony Blair. But within a fortnight, the story had gone somewhere rather unexpected: to a website titled mydavidcameron.com, and an ever-expanding selection of spoof artwork, which cut straight to the heart of not only the poster's absurdity, but the often depressingly empty nature of modern politics.

Initially, Singer – a web specialist and left-aligned political activist – had put up two Cameron mock-ups of his own, but then he watched scores more arrive in his inbox. For a few days, the people responsible used Photoshop; then, unprompted, someone else came up with an easy-to-use online generator, whereby you could simply type in your own slogans, and the programming did the rest of the work.

The result was an avalanche: word spread via Twitter and Facebook, and soon enough, well over 150,000 designs had been created. Some, Singer says, were all potty-mouthed insults and class warfare ("a lot calling Cameron a cunt, and quite a few quoting the lyrics of Eton Rifles by the Jam"). The best, though, had a subtlety that made them very funny indeed: my favourite remains the addition of headphones on Cameron, with the words, "Little Boots, actually."

"For a period of time," Singer tells me, "I was spending most evenings sitting in bed with my partner, just looking at posters. It went viral very quickly: by day eight, we were on about 16,000 unique visitors every 24 hours."

The story ballooned in ways that must have had some Tory high-ups chewing their knuckles. The spoof billboards were picked up by everyone from Sun columnist Jane Moore to the electro-pop quintet Hot Chip. In short order, mydavidcameron.com spoofed two more Tory posters: the dig at Labour's alleged plans for a new "death tax" that features a gravestone, and the new campaign featuring an array of real-life voters and slogans based around the words, "I've never voted Tory before, but . . ." (Suggestions included: "this fox stew tastes delicious", "being unemployed sounds like fun", and "married people are just better".)

In turn, the people in charge of Tory activist website ConservativeHome set up their own clearing-house for anti-Labour spoofs, MyLabourPosters – though in the absence of any high-profile Labour billboards, they resorted to rather unfunny rewrites of Tory posters, some of which were described by marketing website Brand Republic as "really offensive and sinister".

By the end of February, even veterans of the political game were declaring that something fundamental had changed. Michael Portillo acknowledged that, thanks to the first Cameron billboards, any clear Tory message had been "lost in ribaldry over giant images of the leader's face", and Alastair Campbell asked the very timely question: "Has the political poster virtually had its day?" Labour, meanwhile, served notice that it was abandoning high-street billboards altogether – a move largely reducible to the dreadful state of its finances, but it fitted neatly into the bigger story.

As a taste of how this year's general election will differ from every poll that has preceded it, the mydavidcameron.com saga takes some beating. "Increasingly, the attempt to create a very top-down, marketing-led kind of politics is coming under a lot of pressure," Singer agrees. "Suddenly, everyone has a say. I'm cynical about stuff saying that the net has changed everything, but I think that in this area, there is a democratising process."

Gordon Brown in a spoof poster from mylabourposters.

In 2005, the general election was run according to the usual conventions. There was the odd tactical voting site, aimed at giving Labour a fright (I co-ran sonowwhodowevotefor.net, based on the book of the same name), a smattering of election-related blogs, and the usual online coverage from big media outlets – but by and large, events had a very analogue flavour. YouTube was only two months old; Twitter and Facebook weren't even invented.

Back in the 1980s, the main parties grasped the tightly controlled ways of media manipulation – and give or take such wheezes as John Major's famous soapbox, every Tory and Labour campaign since has followed much the same template: presentational gloss, top-down management, and precious few of the mishaps the political world calls "gaffes".

This time, things will be rather different. Parties, large and small, are enthusiastically using what they still insist on calling "new technology", and rather clumsily adjusting to its implications. Among their other digital endeavours, the Tories are spending a good deal of cash advertising on Facebook, trying to snare the attention of the 23 million Britons said to use it. Labour has promised a "massive" drive for online donations, supposedly modelled on the internet magic worked by Barack Obama, and led by the unlikely figure of David Blunkett.

A blog now represents the minimum required



Both parties have come up with special iPhone apps for their activists (Shaun Bailey, the Tory candidate for Hammersmith in London, has the distinction of being the first candidate with an app all of his own). Ed Miliband, charged with putting together Labour's manifesto, is appealing for ideas online, while for all three main party leaders, catering to the Mumsnet vote seems as important as any of the standard electioneering stuff. While nowhere near the online sophistication of politics in the US, the UK may finally be ready for things that are securely built into American debate: not just internet fundraising and advertising, but viral campaigning, websites run way beyond old party structures, and the kind of citizen journalism that has real clout.

For any serious candidate, a blog represents the bare minimum of what the online world now requires, though such activity brings plenty of danger. As one Labour blogger recently put it, "Blogs, tweets and Facebook are actually more likely to be what loses a party the election than what wins it. One ill-considered email, tweet or blog post by a candidate or campaigner can provide a lot of ammo for the old-fashioned media to shred a party's campaign with." In other words, only one thumb-twitch may lie between a modest local campaign and a big national story.

In October last year, the Labour minister Ben Bradshaw was derided for a crass tweet responding to David Cameron's speech at Tory conference, making reference to his disabled son Ivan and the care he received thanks to "Labour's investment and reform". Then in January, in the close-run seat of Brighton Pavilion, Tory candidate Charlotte Vere was pilloried for tweeting a link to a blog that compared the Green party to the BNP. And last month, in a plotline worthy of The Thick of It, a hapless-looking Labour whip called David Wright became the latest politician to be plunged into Twitter-related trouble, via the hilarious line, "I've never voted Tory because you can put lipstick on a scum-sucking pig, but it's still a scum-sucking pig."

Rather unconvincingly, Wright claimed that an unidentified menace had been "tinkering with my tweets", but for a couple of Labour high-ups, that fate has been real enough: both Harriet Harman and Ed Miliband have recently been the victims of the online naughtiness known as "phishing", whereby accounts are hacked, and tweets can be not just tinkered with but completely made up. At the same time, news surfaced of a web operation called The Year of Collaboration, which had set up unauthorised accounts in the names of scores of MPs and begun tweeting the highlights of their contributions in the House Of Commons.

Twitter is becoming a byword for a chaos that political parties cannot abide. Small wonder, then, that Conservative HQ is said to now insist that any material to be blogged or tweeted must be approved by what a Daily Mail headline called "the Tory Twitter police". The official line is that such vetting applies only to pronouncements on policy, though at least one Tory insider I have spoken to claims that "with some candidates, they want to see everything" – underlining the tension that exists between devolved, spontaneous digital media, and the controlling instincts of big party machines.

Most interest is focused on the blogs and websites that may align themselves with the main parties, but remain outside their direct control. Among the most high-profile are Labour List and Left Foot Forward; the right's most-read outlet remains ConservativeHome, now majority-owned by the money-dripping Tory non-dom Lord Ashcroft (though its two-man staff lay claim to continued editorial independence). To be fair, we should also mention the activist website Lib Dem Voice.

'Technology has broken the old monopoly of comment'

But beyond these outlets lies the great tangle of online sources that may not yet be household names – but that, as in the case of Singer and mydavidcameron.com, could create plenty of heat. And it is mention of the latter that often prompts the most excited talk. "Technology has broken the old monopoly of comment," says Tim Montgomerie, ConservativeHome's co-editor. "Now we're going to see much more interesting monopolies being broken. Certainly, the monopoly of party political broadcasts is over: at this election, anyone can make one, and it's all completely unregulated. It'll probably be some amateur in their bedroom making a funny video – that's what'll take off."

Already, online evidence is there in abundance, from a mildly amusing clip that casts George Osborne in the video for Culture Club's Karma Chameleon (Boy George – geddit?), a brilliantly retooled episode of Thunderbirds titled Webcameronbirds Are Go, to wheezes so well-executed you cannot help but suspect the involvement of political insiders. Last month, a video game appeared online whereby players have to steer Alistair Darling away from the "forces of hell" represented by Gordon Brown, Ed Balls and their former attack-dog Damien McBride – Pac-Man for Westminster anoraks.

Montgomerie mentions another fascinating aspect of how coverage online will alter traditional power balances during the campaign – by focusing no end of forensic attention not just on politicians, but the orthodox media. "It always seems to me that there are lots of cosy clubs where the media don't criticise each other," he says. "That's not going to be true any more. Commentators will be savaged if they do sloppy or unbalanced journalism; people who haven't had to look over their shoulders will be forced to do so."

He says ConservativeHome's habit of rocking the boat may well lead them into sharp critiques of that age-old rightwing bugbear, the BBC. "Certainly, I think one of ConservativeHome's big jobs in the election is to watch the broadcasters. We can go harder on the BBC than the parties can. I'm sure the left will do the same."

When I talk to Paul "Guido Fawkes" Staines, though, he claims "the main way the blogosphere and its bastard sister the Twittersphere affects the political world is still via the traditional media – because the most avid followers of blogs and tweets are journalists." Not unreasonably, he puts his own influence down to "grabbing the attention of the media class – I think I've got the ability to do that, so I can push an agenda."

His key plan for the election is to make his "Guy News" films – pitched midway between the rib-tickling work of Newsnight's Michael Crick and that Saturday morning classic Tiswas, and apparently watched by between 10,000 and 20,000 people – a once-daily online event, at least. His people will be out way beyond Westminster, following both the campaign and media coverage of it. "If we catch candidates doing things they shouldn't," Staines says, "and we get video of it, then it's going to get re-broadcast on TV." When I ask him what he wants to get out of the election, his camped-up answer comes back in a flash: "A good time. And have no doubt: I'll be claiming victory."

Two or three years ago, Guido Fawkes and ConservativeHome were held up as proof that the online world was dominated by the political right. But in the last year or so there has been a rebalancing of forces, as the left has started to find its voice and take aim at the prospect of a Conservative government. As Will Straw from Left Foot Forward puts it, online outlets suit "oppositional" voices better than those trying to make a positive case – as proved by the fact that his own site (a home, as its strap-line puts it, for "evidence-based political blogging") has found its voice via sharp critiques of the Tories.

"What Labour and its supporters have done is position themselves in opposition to the threat of a Tory government," he says. "We had nothing to go on before, but now we can pick apart policy and the possibility of, say, George Osborne being chancellor. I also think it's fair to say that Labour has more young activists, which will mean a bit of difference. There are many, many people online who are engaged in leftwing issues: the environment, development, poverty. When push comes to shove, they'd rather have a Labour government than a Tory one."

Different kinds of activism

While the left and right duke it out, other people are busy with rather different kinds of activism. The team behind a site called The Straight Choice are appealing for scans of local election leaflets, to go into an already-bulging archive – because, as the site's co-founder Julian Todd puts it, "that's where most of the actual campaigning happens; if you want to find out what a political party actually does, that's the place to look." At Your Next MP, another crew of volunteers are putting together a database of every candidate standing, which currently stands at 2,432. ("We are completely neutral," they advise. "You have to make your own choice.")

Both projects are linked to Democracy Club, an enterprise dreamed up by Seb Bacon, a 34-year-old resident of Glasgow. Work is still in progress, but he has already signed up more than 4,000 volunteers. Among the site's founding ideas, Bacon tells me, are "giving people an opportunity to engage with politics in simple, small, achievable ways", "holding politicians to account", and "ensuring there's transparency and accountability at the election".

So you can, for example, discover that landfill is a hot topic in Arundel and South Downs; that a new bypass is desperately needed in North Cornwall; and that "the general condition of rear access roads in Harehills" is big news in Leeds East. Bacon aims to convert all this stuff into lists of questions for each and every candidate, and thereby make a stand for local accountability.

"The other thing is, I'd really like people to vote for candidates because they have some insight into who they are, not just on party lines," he says. "There's going to be a particularly high turnover of new MPs at this election, and I'd like people to be interested in who's representing them. I think people are fed up, rather than apathetic; I want to give people the chance to show that."

Over at mydavidcameron.com, the more mischievous Singer is planning his next move. Having already announced he wouldn't be spoofing the next Conservative ad campaign, he is trying to think of something more ambitious – "maybe involving video" – though no firm plans have yet taken shape.

What struck him about the endless poster-spoofs, Singer says, was how mean-spirited some of them were – particularly those anti-Labour designs. Proof, perhaps, that as an idea spreads online, subtlety and humour tend to fall away, and the prevailing mood usually turns nasty.

"That's what it's felt like," he says. "But maybe there's a simpler explanation: that Tories can't really do humour."