I am grateful to Pete Wedderburn, the "top TV vet" who answers Daily Telegraph readers' questions about animals, for this insight into the 12 months ahead: "There'll be many unexpected events that will occur during the next year." Such as what, Pete? "The news story today about the man whose eyes were damaged by his pet tarantula is a good example."
What a very salutary warning. All predictions about politics should bear in mind the tarantula factor. So when Martin Baxter, a mathematician, puts the probability of a Tory majority at the next election at 62 per cent, we should remember that there are small probabilities of less likely outcomes. Baxter, who runs a website called Electoral Calculus, puts the probability of a Labour majority, based on current opinion polls and the past variability of political events, at 10 per cent. It would take a few tarantulas running amok to bring that about, you might think.
Well, there is still the Bob Hawke scenario – where a change of leader at the start of the three-week election campaign in 1983 transformed the Australian Labor Party's prospects. Under Hawke, the party went on to win a further three consecutive victories. Three of the usual suspects among Labour MPs, Charles Clarke, Barry Sheerman and Greg Pope, published new year messages calling for Gordon Brown to stand aside, in terms almost identical to those of the letter from other Labour MPs to Tony Blair three years before: "Sadly, it is clear to us, as it is to almost the entire party and the entire country, that without an urgent change in the leadership of the party it becomes less likely that we will win ... the next general election."
Unfortunately, it is not clear enough in Brown's case now. Clarke, the former home secretary, said last week that "all the evidence suggests ... that alternative leaders would improve our ratings", when in fact the opinion polls suggest no such thing. Clarke, Sheerman, Pope, most of the Cabinet and I are all sure that Labour would be more popular if Alan Johnson, David Miliband or even Liam Byrne or Charles Clarke were leader. But the polls don't show it. And that is the difference between now and the two recent occasions that governing parties ditched a sitting prime minister, Thatcher in 1990 and Blair in 2006-07, when the polls suggested that Heseltine and Brown would be more popular. The Cabinet and Labour MPs generally are unlikely to force Brown out without that kind of evidence. Something else, something as unlikely as a pet tarantula on the loose, would have to give.
Even if it did, a 10 per cent chance of a Labour majority seems putting it too high. Sure, Labour is doomed if Brown stays as leader; but even if he goes, the best the party can hope for is probably a hung parliament. Baxter puts the chance of a hung parliament at 29 per cent – which gives a total of 101 per cent because the numbers are rounded up. Now, a hung parliament is better than outright defeat, from a Labour point of view, but it would not alter the main prediction of the political year, which is that David Cameron will become prime minister. Even if the Conservatives fail to gain the barest majority (of two, since you ask: in the new House of Commons of 650 members, the majority must be an even number), their leader is almost certain to be invited to form a government. Labour will have "lost" and in any case the Tories will be likely to be the largest party.
So this is a watershed year. The year of at least a 90 per cent chance of a change of government. Tim Bale, in his brilliant study, The Conservative Party from Thatcher to Cameron, observes that in Britain "changes of government are precipitated not by a burning sense of right or wrong but by a vague feeling that things have gone too far in one direction and that some kind of correction is needed to bring them back into balance". Going back to an earlier decade-shift, he says that the voters "got the welfare state from the Attlee government, for instance, but after five years of sacrifice they were longing to do some shopping." Applying that analysis to the New Labour years, the voters take the rebuilding of the NHS, and to a lesser extent the education system, for granted, but want to check bloated government spending, over-regulation and nanny statism.
Today's decade-shift is a kind of opposite case to that of 1950-51, going into a period of austerity rather than coming out.
The big questions for the coming year, therefore, are about the Conservatives and what they would do. I suppose that I ought to be interested in the Labour leadership election after defeat, but I am just not. Theoretically, the unsubtle positioning of Ed Balls, the sibling rivalry of the Miliband brothers and the mischievous role played by Peter Mandelson should be fascinating to political obsessives; in practice, they lack a dramatic sense of purpose. Already, we obsessives are more interested in hints of tension between Cameron and George Osborne, and in the ambitions of Boris Johnson.
And there are big issues facing the next government. What will happen to public spending? Alistair Darling's pre-Budget report last month plans for cuts of 19 per cent in real terms over three years from April 2011 in everything but health and education, and the Tories have said they will cut earlier and deeper (but still exempt health and education spending). What will happen when impossible plans collide with inflexible reality?
And what will happen to the economy? Unemployment has risen much less and shows signs of peaking much earlier than previous recessions would have us expect. If new figures confirm that change, when will inflation become a threat again?
David Cameron, Pete Wedderburn's advice is for you. Make sure that you wear New-Labour nanny-state safety goggles when handling George's pet tarantula.
John Rentoul blogs at www.independent.co.uk/eagleeye