What it would take for the Lib Dems to break through the Labour/Conservative duopoly? My opinion is that the sort of exceptional circumstances that would allow such a thing to happen are so improbable that the possibility is usually discounted altogether.

The last “Leapfrogging” – Labour over the Liberals – emerged from a combination of factors. There wasn’t one person plotting and scheming – events simply conspired to create an inevitability that, once the dominos began falling, proved unstoppable.

But, intriguingly, there are some exceptional factors in this General Election: The previous Government has been the most corrupt in living memory. Ambient disillusionment with politics and politicians has turned into a corrosive loathing and disgust over the expenses scandal. Trust has been destroyed, confidence shattered. That’s the first domino.

The second domino is the decision to have televised leaders’ debates, and the decision to include the Liberal Democrats.

The third domino is Clegg offering a centrist, moderate, anti-establishment protest vote at the exact moment that people, more than anything, want to protest and bring down the Establishment, and the Establishment has granted Clegg a platform to get this message heard. In the debate he managed to make the case that Labour and the Conservatives represent one single organisation, and a sort of selfish power mad parasite on Britain, whilst at the same time making the Lib Dems seem to represent.. well… normal people.

It’s a fiction, of course, but it’s close enough to the truth to make a lot of people believe it… and that’s what’s fuelling Cleggmania. This leads nicely to the fourth domino: The media. Normally, you see, they don’t bother paying too much attention to the Lib Dems beyond what they’re legally compelled to. But this election? Well, there’s a whole new story because of the bizarre polling showing massive support for the third party and the Government falling into 3rd place in many polls. This reinforces Clegg’s narrative, and as it’s repeated so it becomes more and more “true”, which keeps the Lib Dems polling well and we get the 5th domino: The media story becomes, “how will Labour and the Conservatives stop Clegg?” If this were a political thriller being written, that’d be the point of no return.

There’s other dominos (social media being the least predictable) but the biggest and most exceptional of all, the one that absolutely has to fall if there’s going to be a “Leapfrogging”, is also the most terrifying: Imagine Labour fails to recover and Lib Dems remain strong. The poll is held and, despite coming third in the national vote, Labour still wins the most seats. That’s the outcome predicted from the polling taken over the weekend. Suddenly we’d have a major constitutional crisis where the ‘winner’ of the election is the least popular party with the smallest mandate. At that point, if that domino fell, Proportional Representation would become inevitable and that, I think, changes everything.

Of course this is just a story, but the story of this election is strange enough already and has wrong-footed all of us. Every day the bizarre polling continues the worse it’s going to get, too. To my own utter astonishment Mr Clegg has got me half believing he can really do this. More on this to come…