Andrew Grice: The Week in Politics

Threat to Cameron's cleansing of Tory brand

David Davis was the centre of attention at a Christmas party I attended a few years ago. He gave a no-holds barred analysis of the problems afflicting the Conservative Party, including the shortcomings of several of his senior "colleagues". On the way home, my startled son, who hadn't met many politicians, asked: "Are they all like that?"

Mr Davis's undoubted ambition makes his sacrificing of an excellent chance to become home secretary even more admirable. But that is not how his decision to fight his "42-day detention" by-election is viewed by his current Conservative "colleagues". They are seething that David Cameron's apparently easy stroll to a general election victory has been suddenly interrupted.

For weeks, Gordon Brown's allies have been praying for something to shift the media spotlight away from his troubles and the growing debate among his own MPs about whether he is the right man to lead Labour into the election.

Without the Davis bombshell, the political headlines in yesterday's newspapers would have been about the looming revolt over 42 days in the House of Lords and the grubby deals Mr Brown did to squeeze the measure through the Commons. Instead, most headlines were about Tory turmoil and splits, something Mr Cameron hoped he had put behind him. A furious Tory leader must now mouth support for his former shadow home secretary, as he is fighting his by-election on the party's policy of opposing 42 days.

Mr Cameron's game plan for winning power is based on being on the right side of public opinion, not the wrong one. That is why, while persuaded by Mr Davis to oppose the measure, he didn't want to die in the ditch for it – or see the issue dominate politics.

The Cameroons fear the Davis gambit will harm the party. "The issue for us was not a number of days of detention. It was supposed to be about Gordon Brown. Now it is about us," one said yesterday.

Mr Cameron will be keeping his fingers crossed that the "DD by-election" is a temporary diversion, that normal politics will resume shortly. He may be right because economic woes will remind voters that Mr Brown's greatest strength has turned into a potentially fatal weakness.

But nothing is certain in politics, as this week's extraordinary turn of events shows. The danger for Mr Cameron is that voters turn their attention to the Tories not at the moment of his choosing, but to witness a farcical by-election and a party whose tensions and divisions are visible again.

The Tory leader has worked overtime to decontaminate his party's brand. The Cameroons were influenced by polling in 2005 showing that 64 per cent of people approved of the immigration policy favoured by the Tories – but that the figure dropped to 30 per cent when they were told it was Tory policy. "The brand poisons the products," concluded the pollster Andrew Cooper, a former Tory official who is director of Populus. He plays down fears among some Tory MPs that the Davis saga could "recontaminate" the party, believing it will be a passing problem. The return of "Tory sleaze" amid rows over the expenses claimed by Tory MEPs poses a much more dangerous threat, he believes. Some senior Labour figures fear the two main parties have changed places, that Labour is now contaminated after 11 years in power.

An ICM survey before the Commons vote on 42 days found that 65 per cent of people support the proposal, and yet the Tories are four points ahead when they are asked which party has the tougher policies to fight terrorism."We are the contaminated brand now," one minister told me.

Mr Cooper thinks otherwise. Although people have tired of Labour, he suspects that many think the party still has positive motives. "On the other hand, the brand of Gordon Brown is totally broken," he said. That is why Labour MPs and ministers agonise about whether to try to force him out.

In the short term, the Commons' approval of 42-day detention and the Davis episode will relieve some of the pressure on the Prime Minister. The one ray of hope in the Brown camp is that the Tory leader has not yet added positive support for the Tories to the anti-Labour sentiment. Indeed, some Tories fear that the party's opinion poll lead is "soft", that its 40 per cent rating could drop to 30 per cent because it has not yet been entrenched.

Voters believe Mr Cameron has changed his party. When asked how, many reply: "They are united now." So headlines about Tory splits ahead of the by-election on 10 July could do damage. The polls and focus groups also show that some people believe the Tories elected Mr Cameron because he was the figure most like Tony Blair, and doubt that the whole Tory party has changed. There are underlying fears over whether he is strong enough to keep his party in check.

At the election, Labour will try to detach Mr Cameron from the rest of his party, claiming it is "the same old Tories" underneath. This is why the next four weeks will be as much a test for Mr Cameron as Mr Davis. He will doubtless face up to it, but it is not one he welcomes.