Bruce Anderson: In offering Labour an illusion of hope, David Davis may have done Cameron a service

Politicians whose views alter in middle life are always fascinating, and hazardous

A week ago, British politics was almost on the verge of becoming dull. Labour was bound to lose; the only question still to answer was the size of David Cameron's majority. That was the consensus – in the Labour Party. The cloud of defeatism had settled on Labour MPs, who were even more mired in the slough of despond than their Tory counterparts in 1996/7.

There were even suggestions that this was affecting the Prime Minister. At PM's Questions 10 days ago, as one Labour MP put it, "he looked forlorn". He could hardly put up his fists to defend himself against Mr Cameron's battering. Some Tories even wondered whether he was trying for a sympathy vote: "Puir Scots laddie beaten up by public school bully". The great clunking fist becomes pitiable; who would have thought it. It is almost as implausible as the notion that Labour would receive, and welcome, the kiss of life from David Davis. Now, everything is in flux. So what will be the outcome? Almost certainly, it will be less significant than the inhabitants of Westminster believe. The latest poll, which shows a 22-point Tory lead, suggests that the voters' dislike of the current government is too deep for David Davis to root out.

Much will depend on the way in which the Davis by-election is conducted. He intends to fight it on civil liberties, but single-issue campaigns always tend to become broader. Mr Davis might decide to add the European referendum to his list of spurious vindications. If so, that could help the Tories. But given the instability of the Davis ego, anything is possible. The Tory party still harbours a few malcontents and fantasists: people who want to leave the EU altogether and slash taxes instantly, irrespective of fiscal reality. These characters will try to foist their agenda on Mr Davis while proclaiming him to be a parliamentary hero. This could be tricky for Mr Cameron. If poison for the Tory party were offered in a strong cocktail of flattery, the risk is that David Davis would drink it.

There is a further problem. Politicians whose views alter in middle life are always fascinating, attractive and hazardous. Fascinating to commentators, attractive to opponents; hazardous to those trying to manage the political party to which the mind-changer owes nominal allegiance. It seems curious that David Davis should have reinvented himself as a libertarian. Rarely have a man's opinions seemed more at odds with his personality. But a senior politician who becomes a convert to a new cause is like a large ship which breaks from her mooring. Where will the voyage end? And what will be wrecked along the way?

Even without David Davis in erratic orbit, the liberty issue is awkward for the Tories. On the one hand, this Government has greatly increased the power of the state, giving petty officials all sorts of entitlements to interfere with the ordinary citizen. This government has reinvented Little Hitlerism. A vice to which minor civil servants are especially prone, this crept into public life during the war, when any interference with liberty could be justified by "don't you know there's a war on?" From the 1950s onwards, the scourge of Little Hitlerism was steadily reduced, but never eradicated. Some branches of the public service attract those who enjoy bossing people about.

The Brown Government has given them plenty of scope to do that. One of the first measures an incoming Tory government should implement is a thorough review of all the recently increased powers, leading to an extensive cull. But there is an obvious problem. It would only take a couple more terrorist bombs and "don't you know there's a war on?" might recapture the power to quell the spirit of contrarianism and reinforce obedience.

Last Wednesday, Gordon Brown reminded David Cameron that according to the opinion polls, a majority of voters supported 42 days. Even by the standards we have come to expect from this Prime Minister, that was contemptible. No government worthy of the name would allow opinion polls to take decisions on national security. In response, Mr Cameron was robust. "It is popular to announce that you are going to bang up terrorist suspects for longer without charging them. He is right ... but ... we in this House are meant to do what is right."

David Cameron was right, and in normal circumstances, voters could come to respect a politician who insisted that he would lead opinion rather than follow it. But a terrorist threat is not normal circumstances. The poll vote for 42 days reflects an electorate which feels fear and is ready to lash out at its enemies.

In that respect, David Davis is a loss to the Tory front bench. His body language is anything but wimpish. He has the ability to inspire trust among the fearful. The new Shadow home secretary, Dominic Grieve, is a lawyer, and sounds like one. Precise, intellectual and bespectacled, he has a significant shareholding in pedantry. Far too often, he talks as if he were an interlocutory order and looks like a mute at a Victorian funeral.

The Tory front bench still faces the challenge which, for all his bluster, David Davis ducked: how to reconcile liberty and order. At present, voters are instinctively on the side of order. They are worried about being blown up. They are less concerned about the arrest of protesters against the nonsensical cult of scientology.

For all his faults, David Davis could have been useful in the struggle to persuade the public that freedom and safety are compatible. In Mr Davis's absence, David Cameron will have to play a major part in that argument. He must ensure that his party can never be accused of being soft on terrorism. He ought to realise that in 10 Downing St, there is a Prime Minister who is waiting for another terrorist outrage, so that he can profit from it. Mr Cameron must ensure that Mr Brown never profits from a cynical and hypocritical attitude to national security.

Because of David Davis, a Tory victory seems less inevitable than it did last Wednesday. But it is unlikely that there has been a significant or lasting shift in public opinion. Out in the country, people are worried about their mortgage rates and living standards. Over the past few months, they have ceased to believe that this Government is acting in their best interests. Indeed, they have stopped listening to the Government.

In 1996, some wise Tories, including Alastair Goodlad, then Chief Whip, and the then Leader of the Lords, Robert Cranborne, concluded that the Tory government was doomed. Whenever the election came, their party would lose it. But the danger was that the longer the Tories hung on, the worse the defeat would be. The electorate would come to regard the government as the overstaying guest who ignores all hints to go home: the wife hissing at the husband: "Has he not gone yet? No, don't open another bottle. If you do, I'll divorce you'." If the Tory party had recognised the need to divorce itself from government in 1996, the ensuing defeat might have been less catastrophic. Forty or so Tory MPs who lost their seats might have held them.

Despite recent excitements, Labour is in a similar position today. So it could be that David Davis has done David Cameron a long-term service. By giving the Brownites the illusion of hope, Mr Davies has prevented them from confronting reality and ensured that their eventual defeat will be even heavier.