Between the idea

And the reality

...

Falls the shadow.

Thus TS Eliot, writing in 1925, predicted how most advertising executives would feel most of the time. But perhaps particularly those working in politics.

Advertising deals with stuff that is (at least) at one remove from reality. And the live debates have proved that more than anything I've seen before.

Prior to the live debates, everything looked relatively straightforward. Tory would bash Labour, Labour would bash Tory slightly less cruelly, and the Lib Dems would try to bash both of them, but get ignored like a six-year-old sibling trying to get in on a pair of 10-year-olds' pillow fight.

Richard Huntington, working on the Labour account at Saatchis, emailed me 10 days ago to say: "We are yet to witness a defining piece of work from any of the parties. We may yet though."

At the time I thought he just meant that a magnificent piece of mud-slinging was about to come out – after all, Hague in a Thatcher wig was a defining piece of work.

But then Clegg, as the Guardian put it, seized his moment. And what really interested me was that the debates brought some reality to what had previously been a sort of shadow debate, happening on the poster sites.

The debates have been a huge surprise. First, that we watched them at all. All the pundits were predicting death by boredom. And more people watched a TV programme called Young Butcher of the Year (a sort of "Butcher Idol", if you can imagine that) than watched a live debate between the candidates for the next chancellor of the exchequer.

Second, that Cameron has fared so badly. It was his initiative in the first place, but as Bell Pottinger chairman Peter Bingle claimed, the televised debates may well have cost the Conservative party the election: "Whichever adviser or guru advised David Cameron to take part made a terrible mistake."

If you want some real science go to the highly addictive Slapometer site, where Cameron polled an impressive and doubtless rather painful 50% of the total slaps given to all three leaders. On both debates.

He really has struggled. We all expected him to be cool and razzle-dazzley – like Tom Cruise being interviewed by Jonathan Ross. But he came across as Jonathan Ross being interviewed by Jonathan Ross.

And we all expected Brown to look like a breed of Highland cattle plop-plopping mournful excrement. He's done a lot better than that, although last night, in HD, you could see the pancake thick on his face.

There were some extraordinary moments last night. Cameron saying: "A politician shouldn't say 'lies' very often." Nobody else seems to have commented on that so far, so maybe I was hallucinating.

But the combination of childishness and evasiveness was too good not to be true, I thought. And Gordon saying he hadn't authorised the pensioner-scaring leaflets. There spake a man who accepts responsibility as readily as a child in a game of pass-the-parcel.

Although Cameron's accusation of scaremongering was like Nick Griffin accusing someone of racism. What about his scarey posters of tombstones?

Or, even more frighteningly, his posters of Gordon smiling?

I loved Clegg's dig at Cam's alliance with climate change deniers, antisemites and homophobes. Cameron's face at that point would make a good 48-sheet poster for the Lib Dems.

But the reality was that Clegg's performances have brought him to the forefront of the picture. So I found myself looking at his marketing to see how he was approaching it all.

One agency called The Assembly has done a PEB for him about broken promises (which I thought was very good, but which could have done with more examples), while another agency called Iris was doing a spoof of Brown and Cameron and a host of other "Labservative" leaders.

Assembly's work had more substance, but Iris's approach seems to be the one which has initially worked. By lumping his two opponents together, and poking fun at them, Clegg has won hearts and minds nationwide.

Why two agencies? Lack of funds. While the Tories can (and usually do) fire agencies with all the aplomb of billionaires switching mistresses, Clegg is forced to accept hand-outs from anybody willing to help.

But his message has nevertheless come shining through. He's nicked Cameron's position of "change" – and anyway if Cameron wanted change, he's got it. Eighteen months ago, he was 26 points ahead in the polls.

So, how have the other parties responded to the two-horse race turning into a three-legged race (with all that that implies)? Labour has released a film with Eddie Izzard. He reminds us that the Tories are Thatcher's children and advises us to: "Be afraid. Be very afraid."

The bit I didn't like was where he talked about meeting lots of people on his marathons who backed up his belief that Britain was doing all right.

Yes, it's more credible than Cameron meeting a 40-year-old black man who doesn't want any more immigration. But insisting that you keep meeting people who agree with you, has always been a sure sign of madness.

They also made a film purporting to come from the future and portraying a society damaged by Conservative rule. As a complete contrast to that, the Tories kicked off a Twitter feed purporting to come from 2015 and – well, you've guessed the rest, haven't you?

Do they really think we're gonna fall for stuff like this ? Sadly, they do.

The Tories also produced a very bland PEB, whose only highlight was David Cameron screaming "When will shopkeepers stop selling alcohol to kids? And will you turn that bloody music down?"

(I'm exaggerating slightly. I have to. It was too boring for words.)

Then they ran a couple of posters that are so boring it's barely worth discussing them.

All of which backed up the live debate statistics on aggression. Brown went on the offensive 21 times last night, Clegg 14 times and Cameron only 11 times. The Tories really are hamstrung by the fear of being seen as bullies. At last, something good has come out of political correctness.

Although, give them credit. They're trying to be aggressive. One of the posters read: "Let's stop Labour's jobs tax." A spokesman said: "These posters are part of our positive campaign to show the public why David Cameron and the Conservatives have the right values." Positive? Only in the context of political advertising could a poster that attacks your opponent and offers no alternative be termed positive.

But advertising has been the loser in this election. Mud-slinging billboards haven't had a tenth of the impact of the live debates. As I said at the beginning of this, that's one of the problems with advertising. It's always been about selling "the "sizzle, not the sausage".

I've always suspected that this showed a lack of trust in the probity of the sausage. And in the long history of political advertising, and politics generally, that may well have been valid. But with Clegg, maybe, finally, there really is some beef.