DJ Taylor: The tribes, they are a-changin': ask any Essex girl like Boudicca

Spotting election posters shows that old political certainties no longer apply, in Norwich if not in Cornwall; how Labour's determination to reform the Lords could backfire; the Feelgood factor; and teen egg rage

To walk for even a few minutes through the constituency of Norwich South – its car-clogged council estates, its tree-lined bourgeois thoroughfares, its bed-sittered student terraces – is to be made sharply aware of how little the old tribalism endures.

Thirty years ago, the political demarcations of Norwich's real estate were set in stone. Leaving our front door at election time, one wandered west through clumps of Conservative posters until the council houses began, whereupon the posters changed abruptly to red. Beyond Colman Road, half a mile away, there were stretches of mixed housing, where the demographic veered from owner-occupier to municipal-renter from one street to the next, with the banners dutifully following suit. There were, of course, always fewer Conservative placards, on the excellent grounds that these were likely to be smashed up during the small hours and the fragments thrown back over one's garden fence.

If this ability to predict how people were going to vote rested on the kind of house they lived in, then it also extended to the careers they pursued. I don't recall a single parent of the boys I was at school with voting anything other than Conservative, except perhaps a university lecturer or two quietly favouring the Liberals – a piece of whimsicality more or less on a par with having your front door painted purple. My father was a boy from a poorish home who won a council scholarship to the local private school and acquired a white-collar job. My mother was the granddaughter of a shopkeeper in a Suffolk market town. It was inconceivable that either of them would have voted for Harold Wilson, whom they regarded as shifty and in thrall to the militant left, or Jeremy Thorpe, whom they thought simply irrelevant.

Three decades later, the old certainties have been blown apart. A stroll down the top of Unthank Road, one of Norwich's classiest residential quadrants, reveals a panorama of Green Party banners and Lib Dem exhortations, with barely a Tory poster in sight. Even my father, towards the end of his life, abandoned the Tories at least once for Ukip on the grounds that the former were, as he put it, "poor boys". I have no idea how my mother will be voting, but I doubt it will be for David Cameron. If it comes to that, this long-time member of the Labour Party has serious doubts about Gordon Brown.

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On the other hand, there are some areas of our national life where aspects of the old tribalism are still going strong. Driving back from Cornwall a few days ago, past field upon field bearing pictures of the well-lunched faces of Tory MPs, I asked the children if they could account for this bias. "Because farmers are Conservatives," one of them volunteered. True or false? Certainly, there can't be many cultivators of the rolling West Country arable getting ready to vote Labour, but how does the average Welsh hill-farmer place his cross? Or a Gloucestershire apple-grower watching his 100 acres being steadily squashed into insignificance by the giant agribusinesses on either side?

The urge to track political affiliations back to livelihood has deep historical roots. George Orwell, for example, once suggested – with apparent seriousness – that "all tobacconists are fascists". Malcolm Muggeridge later wrote an amusing critique of this statement, starting with the premise that this was one of Orwell's trademark unprovable assertions, but then getting gradually seduced by the effrontery of it, and concluding that, yes, there really was something rather strange about all those intent, brooding little men cooped up in their fag-lined hutches, and perhaps they were a legion of right-wing fantasists. No coincidence that Pierre-Marie Poujade, leader of the French political movement that bore his name, was a small shopkeeper. Somehow you doubt that there are many social groups whose members can still be characterised in this way, or even political parties where any kind of blanket unanimity prevails.

I can remember being highly amused by a World in Action documentary from the strike-bound 1970s which demonstrated that a fair number of coalminers voted Conservative. No doubt the Campaign for the Preservation of Rural England has its fifth column of property developers, and the British National Party its "liberal wing".

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The week's most depressing political moment undoubtedly came in the interview granted by Gordon Brown to The Independent, in which he talked of his desire to forge a new "progressive alliance" aimed at keeping the Conservatives permanently out of office. Judging by the opinion polls, the voters are unimpressed. The word from the political columns is that several of Mr Brown's cabinet colleagues have similar reservations. Naturally, one of the great unwritten laws of politics is that party leaders, overcome by the pressures of the moment, have a habit of saying things they will later come to regret, but it would take an extensive trawl through recent political history to find anything quite so wantonly opportunistic.

How many times in the past three years has Mr Brown noticed that Lib Dems even exist, much less wanted to form a progressive alliance with them? Then there is his much-advertised conversion to constitutional reform and the idea of an elected upper house, which by an unhappy coincidence came the day after the phalanx of ministers formed before the cameras outside No 10 to discuss the transport crisis was found to include My Lords Mandelson, Adonis and West. With 11 days still to go, there is no way of guessing who is going to win on 6 May, but it can be safely predicted that Mr Brown is going to lose it.

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Curiously enough, the pleasure I got out of watching Oil City Confidential, Julien Temple's wonderful film about the Seventies rhythm and blues combo Dr Feelgood, on BBC4 stemmed less from its musical interludes than from the metaphorical torch-beam directed on a certain kind of East Anglian culture. The Feelgoods (Wilko Johnson, John B Sparks, the late Lee Brilleaux and an enigmatic drummer known as "The Big Figure"), were memorably described by the New Musical Express as "the kind of characters you find in a pub you walk into by mistake and then walk straight out of again". They hailed from that most recherché redoubt of the East of England boondocks, Canvey Island, on this evidence a kind of retirement home for East End gangsters.

But Canvey's isolated, end-of-the-line atmosphere is reflected elsewhere in a county where London overspill and rural sequestration, doubtful modernity and cultural atavism, endlessly combine – a 21st-century equivalent, perhaps, of the medieval "debatable lands" of the Scottish border. I wasn't in the least surprised, for example, to find out from the East End novelist Arthur Morrison's Cunning Murrell (1900) that Essex was one of the last redoubts of witchcraft. Even the library at Saffron Walden in the leafiest part of the area, far away from the relocating pearly kings, is full of true-crime confessionals by people with names like Nosher Stribbs. No doubt about it, Boudicca, racing over the fields near what is now Colchester to confront the Roman hordes, was the original Essex Girl. Jowl by jowl, black hides gleaming beneath the pale East Anglian moonlight, the "Essex Dogs", to borrow the title of a memorable poem by local lad Damon Albarn, roam effortlessly on.

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The most cheering symbol of this week's politicking was undoubtedly the egg thrown at David Cameron as he went canvassing in Saltash, Cornwall. Tyler Dixon, the 16-year-old trainee bricklayer who threw it, though apprehended by the police, was later released without charge. The egg itself is reported to have bounced off Mr Cameron's shoulder and spattered a policeman with goo. Mr Cameron is thought to have laughed off the incident with the comment that he didn't know which came first, the chicken or the egg – a reference to the Daily Mirror's stunt of hiring a man dressed in a chicken's costume to follow him around the campaign trail.

All at once, a faint scent of the Victorian hustings was blown tantalisingly into the air – an era in which potential MPs, addressing their electors, could expect to be pelted with a variety of missiles ranging from half-bricks to rotten vegetables hoarded over the preceding weeks and dead cats. There is a terrific moment in Trollope's The Prime Minister in which, such is the level of partisanship in the Silverbridge by-election, that one candidate stalks the other with a horsewhip: even at the staider end of the Victorian age, defeated candidates were routinely thrown into duck-ponds. While nobody wants an (allegedly) democratic contest to descend into a free-for-all, my sympathies are with the egg-thrower, Mr Dixon, for daring to make the kind of protest which, by and large, the ballot box denies him.