Michael Brown: It would be rash to forecast that Gordon Brown will never be PM. But it's worth a bet

For most political commentators, 2005 will go down as one of the most tumultuous years certainly since the 1997 general election and possibly since the fall of Margaret Thatcher in 1990. On the face of it, however, the year is ending as predictably as it began. Labour was safely returned for another term and Tony Blair remains Prime Minister. And relations between Gordon Brown and Tony Blair are as strained as they were a year ago. Still there is no answer to the question that dominates the Labour Party: when will Gordon take over from Tony?

Yet looking at the past few days of television news reviews of the past 12 months, the general election campaign itself was actually perhaps the most forgotten event in the political calendar. No one doubted that Labour would be returned, and the only egg was on the faces of political pundits as we were confronted by the extent to which our prophesies overestimated or underestimated the size of Mr Blair's Commons majority. The real story, that only a few of us anticipated, was the scandal that the current electoral system could reward a party, with less than 36 per cent of the vote, with a large - albeit reduced - majority.

These days between Christmas and New Year are a nightmare for our profession as we are cruelly reminded of some of the more bizarre forecasts that we made in unguarded moments in previous columns and TV programmes. Every December, I am asked by fellow Independent columnist Steve Richards, on his GMTV Sunday programme, to make a couple of political predictions for the ensuing 12 months. Steve and his production team then have great fun playing back, a year later, the nostrums that his guests foolishly utter on his sofa. My general election prediction in 2004 was a Labour majority of 50.

But I have a far more serious dollop of egg on my face following the prediction I made a year ago about who might today be leading the Tory party. I suggested then that the next Tory leader might not even be in the House of Commons and noted that, on this basis, the prospective candidate for Kensington and Chelsea, Sir Malcolm Rifkind, could be the leader. At first, Sir Malcolm did not let me down and lost no time in launching his bid but, by the time the race was due to start, he had not even bothered to leave the paddock. I comfort myself with the thought that I cannot see any serious prediction from a year ago that envisaged that David Cameron would now already be the Tory leader.

My GMTV predictions to be played back to viewers in December 2006 are already in the can. But I am prepared to reveal them to readers of The Independent. And I am already scared I may have made my first mistake. I have stated that Charles Kennedy will no longer be the leader of the Liberal Democrats, but that Mr Blair will still be the occupant of No 10 Downing Street 12 months hence. While I am reasonably certain that my Lib Dem forecast will be fulfilled - possibly after the party's spring conference in Harrogate - I am having second thoughts about Mr Blair's longer-term Downing Street tenancy.

The key to both these predictions' accuracy depends on the Tory leader, David Cameron. If the Leader of the Opposition continues to capitalise on his political honeymoon, and the current small Tory lead becomes entrenched, this will induce the panic that will be the motor driving both the Lib Dems and the Labour Party. So far, just Mr Cameron's existence appears to be the justification for the Lib Dems taking leave of their senses and handing the Tories a propaganda coup. Charles Kennedy has, in polling terms, actually turned out to be the most successful leader of his party for 80 years. But Mr Kennedy is a wounded animal and if his deputy, Sir Menzies Campbell, were minded to strike, as the senior man in the grey suit (or perhaps I should say, as befits the Lib Dems, grey sandals) then there would almost certainly be a leadership ballot.

But Sir Menzies cannot guarantee that the membership - the final arbiters in these matters - will vote for him or his chosen candidate. There is a serious risk that Simon Hughes would be the membership's choice and this would enable the Tories to portray the Lib Dems as firmly on the left of the political spectrum. If, however, one of the younger breed of Lib Dems - David Laws, Nick Clegg or Mark Oaten - or even Sir Menzies himself - were to succeed, the Tories would face stiffer competition for the anti-Labour vote.

But the seminal change in opposition politics since Mr Cameron's arrival is the Tory threat to the Lib Dems. The new Tory leader may therefore indirectly have it in his power to hasten the demise of Mr Kennedy should he feel that he wants this scalp. I suspect that the temptation to help Mr Kennedy depart will prove strong for Mr Cameron, but there is also much to be said from a Tory viewpoint for leaving a wounded Kennedy in place for as long as possible.

The same argument applies as to when Mr Blair should be replaced - and whether it is in Mr Cameron's interest for Mr Brown to take over the Labour leadership sooner rather than later - or, indeed, if it is in Mr Cameron's interest to face Mr Brown at all. In theory, none of the decisions on the alternative outcomes are in Mr Cameron's gift, yet in practice they may well be. The decision as to whether to allow the Prime Minister to secure education reform on the back of Tory votes puts Mr Blair in the position of Ramsay MacDonald; a Labour prime minister in office thanks to Tory votes. Labour would then be irrevocably split and John Prescott would be able to administer the lethal injection to the Blair premiership.

Mr Prescott has it in his power to pull the plug on the Blair premiership whenever he chooses. The negative power of the Deputy Prime Minister becomes more potent every day during the remaining period of the Blair premiership. But Mr Prescott might be looking as nervously as Labour backbenchers, in marginal constituencies, at poll suggestions that the Cameron Tories may beat Labour under Brown. So watch out for any signs that the Prescott/Brown relationship - normally as cordial as the Brown/Blair relationship is strained - shows any sign of breaking down.

Mr Cameron's Christmas card emphasises "change, hope and optimism". If he fulfils this promise to his party in 2006 then, indirectly, he will determine the fate of Mr Kennedy and Mr Blair. It will be down to others, however, notably Sir Menzies Campbell, Gordon Brown and John Prescott, to call time on their party leaders. I still stick with Blair to stay and Kennedy to go. But it will be the unexpected and unplanned events that will make redundant all our attempts to accurately crystal-ball gaze. Only uncertainty is certain in politics. And dare any of us be brave and predict that Mr Brown will never be prime minister. I'll desist - but it's worth a secret bet.

mrbrown@talktalk.net