AT FIRST sight, Gordon Brown might not seem to have much in common with Tigger. Owl, possibly, Eeyore, perhaps, but not Tigger. Yet the “Tigger Factor” will determine the fate of British politics. For, as we know, “bouncing is what Tiggers do best”. The question now is what sort of upward movement Mr Brown can achieve in the polls when he finally assumes office from Tony Blair and for how long he can sustain it.

There is, admittedly, the matter of a party leadership competition to contend with before he starts to imitate a character from Winnie the Pooh. But the moment of worst danger for Mr Brown may, in my view, be passing. The trouble with the “Anybody but Gordon” movement is that the rules demand a “Somebody other than Gordon” option.

Alan Johnson, the Education Secretary, is wisely doubtful about sacrificing a decent shot at the Deputy Leader slot for a wildly risky bid to climb higher. John Reid, the Home Secretary, is an admirable chap but — despite the incentive of Lord Hattersley promising to top himself if Dr Reid were to win — he does not have a sufficient base in Labour’s electoral college. Charles Clarke, ordinarily a reasonable figure, seems to have acquired the political version of Tourette’s Syndrome. There is still Alan Milburn, but the party constitution asks for 44 MPs to endorse a nomination, not four of them.

All that Mr Brown has to do in his speech to the party conference today, therefore, is praise the Prime Minister to the hilt, talk warmly of his colleagues, urge party unity with passion, remind delegates that he shares their values and then sit down. He should be able to manage that. He remains the overwhelming favourite.

But is he Tigger? Or is he more like one of those space hoppers, toys that offer the illusion of great bounce while usually taking those who ride them no higher than if they had simply jumped up and down on the spot? The consensus of the professionals — articulated by Andrew Cooper in these pages on Saturday — is that Mr Brown is not destined to gain serious momentum. I disagree for three reasons.

The first is that every midterm switch of prime minister since 1945 has led to some sort of “bounce” and that this has rarely been predicted beforehand. Voters look at people in a different way after they have become a party leader than they do when asked in advance what they might think of them in that position. History has bequeathed us a consistent pattern.

Anthony Eden obtained a four-point lift in 1955 and cashed it in straight away with an election victory. The Tories ended up six points higher in the 1959 hustings than they had been before Harold Macmillan took over in 1957. The seemingly dull Sir Alec Douglas-Home put up his party’s rating by seven points in the 12 months between 1963 and 1964 and almost pulled off an unlikely triumph. Jim Callaghan took Labour from 41 per cent in 1976 to 48 per cent by late 1978 before making the catastrophic decision to defer meeting the electorate until 1979. John Major piled on eight points for the Tories between Margaret Thatcher’s fall and the 1992 showdown. A bounce always occurs but it is almost never anticipated by opinion surveys, media focus groups or other types of black magic.

A more recent example reinforces the evidence. For most of last summer David Cameron trailed Mr Brown when voters were asked to make a theoretical selection between them if they were the leaders of their respective parties.

Even after his address to the Conservative Party conference catapulted him into the limelight Mr Cameron again ranked second best to the Chancellor. Only once he became the Leader of the Opposition, while Mr Brown was merely a potential prime minister, did Mr Cameron open up any kind of advantage. Incumbency alters public perceptions. With deep respect to the pollsters, whom I admire, they are making their assessments irrationally early.

The second reason why Mr Brown may have more spring in his tail than it seems is that, as Prime Minister, he can launch initiatives that appeal to the Left without alienating the centre. The broad themes of his opening 100 days can be predicted. Constitutional reform will be embraced, along with a crackdown on anything that smells of political corruption.

A timetable for removing troops from Iraq will be outlined, while new weight is placed on fighting world poverty rather than invading nations in the Middle East. A moral tone with an emphasis on integrity will replace the Hello! magazine style of the Blair era. Who in the centre will oppose stomping on dodgy practices, feeding the hungry or austere sincerity? The final factor is that there are plenty of fish in the electoral sea for Mr Brown. Not only are there those who have drifted away from Labour towards the Liberal Democrats, but others who have defected to minor parties and a far, far larger number who abstained in the past two elections.

Only 61 per cent of people cast their ballots in 2005. Some of those who did not are, unfortunately, permanent outcasts from the political process, yet it is irrational to assume that none of them can be enticed back into polling stations. If Labour moves too far to the left in terms of substance it will imperil its prospects. And if it does not change enough in its agenda and style, it will experience no revival. The Chancellor, uniquely, offers the optimal combination.

The true challenge for Mr Brown may not be securing his “bounce” — which could be bigger than he might hope — but avoiding relying on it to endure. He should be ready to call a general election well before 2009, let alone 2010. If he is unopposed for the leadership, there is an argument for moving as soon as is decent. To waste a bounce by waiting too long to exploit it would be, as Tigger contends, “ri-diccorous”.

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