The opinion polls have been strange lately, the behaviour of the political parties stranger still. Or is it the other way around? The polls can't say, the parties don't know. Chicken (headless) or egg (cracked): which comes first?

Only a few short weeks ago, respected senior Tories (and Lord Ancram) were making themselves available to mutter against the boy Cameron. Was he up to the job? Did he, with all that green waffle and Blairite emoting, actually understand what the job entailed?

A single sales pitch later and Mr Cameron is master of all he surveys. A tax policy stolen from the Liberals, fit only to be stolen again by Labour, has won hearts and minds among suburban voters who will not, for the most part, benefit from the reform. It is Gordon Brown's turn to play the new face of a new Britain in old, familiar trouble.

Only a few short months ago he, too, was master of all - and so forth. Seething Labour MPs had agitated relentlessly for Tony Blair's departure. Mr Brown was elevated unopposed to his party's leadership. Opinion polls, the chicken entrails of the social sciences, said he could beat Mr Cameron in everything from a General Election to a knobbly knees contest.

Now a crack in the woodwork yields Charles Clarke, Lord Falconer, Alan Milburn and other Friends of Blair. They can read polls, too. Mr Brown's difficulty is their opportunity to say that he hasn't a clue and that Tony is already "unhappy". Mr Popular is offering career advice. And all because - the strangest thing of all - the Prime Minister has changed his mind about calling an election of no interest, or use, to the electorate.

It was the polls, say the people who run polls, wot done it. By that crude measure, it was also the polls wot done for Sir Menzies Campbell. As it turns out, swathes of lovely Liberal voters will defect to the Tories at the hint of a tax cut. As it turns out, the level-headed Libs think there's nothing for it but to find their third leader in less than two years.

The polls - and a bit of the backstabbing that goes with being the nice party - have ended a distinguished career. Mr Brown's failure to go to the country has rendered Sir Menzies superfluous. A faction lucky to win 22% of the vote in a real election regards polls at 11%-14%, a two-party squeeze, "the age thing", and rampant personal ambition as new and unfamiliar territory. In summary: the Liberals have panicked.

Tories were doing their chickens-in-a-funk dance during the summer. Margins of error and a bit of media frenzy mean Labour has since gone all to cluck. Now the third party, the electoral chicken feed, brings up the rear. The factor in common to each of these events - nothing to do with running the country, of no relevance to the price of beer or butter - has been "volatility".

That's psephologist's shorthand for "haven't a clue". The pollsters cannot tell us why violent mood swings are sweeping the country, why Mr Cameron is a callow loser one week and a visionary the next, or why Mr Brown can be our rock and anchor this morning and a shifty opportunist this afternoon. "Events" - Northern Rock, Iraq withdrawal, Europe - have exerted no leverage. We're all just a bit volatile, or whimsical, or merely fickle.

It seems to me that the polling companies have a duty to investigate this phenomenon. You can imagine the man with the clipboard. To average, weighted voter: "Haven't you any idea what you believe?" AWV: "Put me down as a don't know."

Sir Menzies, to put it bluntly, has been lost in the shuffle. It was not for want of an idea that the Liberal horse was lost. Had that been the case, the Tories would not have nicked the inheritance tax wheeze and reaped the fleeting benefit. Policy and the pursuit of policy, those quaint notions, did not cause the Liberals to mislay another leader. When the parties play pass-the-parcel with ideas, and when they manufacture synthetic personalities for sale, how is a voter supposed to respond?

Like this. He's a bit old. He's a bit dour. He's smarmy. Wouldn't trust my mortgage with him. Don't like his tie. Can't stand his voice. He's too posh. He's too Scottish. Ooh, look: he's sweating a bit. Ooh, look: he can do a whole paragraph - no earpiece - without notes. He's got a nice-looking wife, kids, cat, handshake. And a tax cut, too?

The parties sow and the parties reap. There is no point in blaming 24/7 media when you strain every nerve to exploit those media. There is no point, either, in grumbling at an opinion poll culture when you crow over every fraction of a notional point won in a tiny sample of people you'll never meet. Or, for a change of pace, decide to assassinate the leader because you believe polls more than you believe in ideas, policy or politics.

The opinion samples will shift again shortly, I predict. I consulted a focus group (me) and it says that Mr Cameron's bouncy castle will be deflated when the Liberal voters he attracted decide that Nick Clegg or Chris Huhne is the next nice, bright, youngish, shiny thing.

The Tories will suffer, too, when it becomes clear that the inheritance tax idea - produced in a moment of crisis, remember - was their best shot. Mr Brown and Chancellor Darling have taken possession of the explosive device and made it safe. That's why, still, they enjoy more trust in economic matters - the polls again - than Mr Cameron and George Osborne.

Sir Menzies will have done the Labour government some service. Clearly, that was never his intention. If his party had managed to keep its nerve it might have guessed that a Cameron ascendancy was the quickest route to a hung parliament. Yet with the election "postponed" - it was never called, so why "postponed"? - the Liberal young turks couldn't wait.

That group might as well be Tories, in any case, for all the actual difference it would make. Some of Mr Cameron's lot would be just as happy, meanwhile, among Mr Brown's lot. The true believers among the latter mob are already as Tory, in any case, as is decent. Convergence, it used to be called. So what is a messy pile-up of political cliches if not convergence?

The Westminster system never allowed much room for novelty. You were permitted, from time to time, to vote for a few things, or against a few things. Now the middle men and women are being removed from the process. Small self-appointed groups, studying small self-selected samples from small handfuls of marginals, make the real decisions.

Is Mr Cameron capable of returning the Tories to power?

Is Mr Brown fit to be a Prime Minister in his own right? Is Sir Menzies a liability or an asset? The polls that drive the parties that drive the polls, taking journalism along for the ride, know all and tell all. About poll-obsessed parties, that is, and party-fixated polls, and political theatre in the Westminster village hall.

Put me down as a "don't care".