London Briefing: One of the great mysteries of the British political scene is the failure of the Conservative Party to take advantage of the open goal presented to them by the many failures of the Labour government.

Nowhere is this more evident than in the area of taxation: everyone knows that Gordon Brown has been raising taxes in all sorts of stealthy ways, yet the Tories are unable to present a simple platform based on tax cuts.

A credible tax reduction strategy should be easy to devise and would be enormously popular. But Michael Howard and Oliver Letwin, the Shadow Chancellor, merely mutter about the possibility of lower taxes should circumstances permit.

The need to differentiate yourself politically has never been more paramount in an era when everyone jostles to occupy the centre ground and Labour pinches the one or two good ideas the Conservatives have put forward. The one policy package that Labour cannot copy is one that involves cuts in both taxes and public spending.

Alastair Campbell, Tony Blair's erstwhile press secretary, casts a long shadow. The propaganda war waged against the Tories has been uniquely successful: any suggestion that the Conservatives will cut taxes is immediately greeted with universal condemnation of the associated cuts in public spending and the inevitable decline in health and education provision.

On this line of logic, all of the money thrown by Labour at public services has been well spent and any suggestion that much of it has, in fact, been wasted is laughed out of court.

The facts, of course, are quite different. There is plenty of scope to rein in wasteful increases in government spending and use the money to cut taxes. But such is the strength of Labour's spin machine - and the inability of the Tories to mount a credible challenge - that nobody is willing to argue this simple case.

Nobody trusts Tony Blair very much these days, but it seems that even fewer people are prepared to put much faith in the promises of the Conservatives.

The Liberal Democrats are rubbing their hands with glee at the prospect of taking the seats of several members of the Opposition cabinet, including that of the shadow chancellor.

All of this comes at a time when Blair looks weaker by the day. Many commentators think that his nemesis will be the European constitutional referendum - still probably at least two years away - rather than the looming general election. If held today, that referendum would reject the new constitution by a very wide margin and few political analysts can see how Blair could credibly carry on in the wake of such a humiliating defeat.

I suspect that these commentators will be again surprised by Blair's single-minded determination to cling to power for as long as possible.

More prosaically, the Tories have missed another glorious opportunity to capitalise on another deeply unpopular Labour policy, namely the introduction of identity cards.

The loss of yet another cabinet minister has not hurt Labour one jot, but ID cards could - or should - be a different matter. This move will be hugely expensive with a lot of the money destined to come out of the pockets of individuals. Michael Howard has simply accepted ID cards as a necessary part of the war on terror, the logic of which mystifies most commentators.

The leader of the Tory party is beginning to look tired, even resigned to his fate. Talk has already switched to his post-election fate: should he resign immediately or stay on in a caretaker capacity given the lack of obviously better candidates? While he has made no impact on the opinion polls, it is a mark of the dire straits that the Opposition finds itself in that Howard is deemed to have done a much better job than either of his two predecessors.

Failure is OK, apparently, provided it isn't as big a disaster as before. More than one analyst has observed that the Tories almost seem content with their demise.

Perhaps it really is all down to the economy. For as long as growth and employment hold up, any attempt to assault Labour's lead in the polls is doomed to failure. This might explain the resigned air of the Conservatives and their inevitable defeat.

Labour too seems to have learned this lesson: you can get away with anything provided your economic luck is maintained.