Andrew Grice: The Week in Politics

Boris Johnson, the Tory candidate for mayor of London, buoyed up his party at the start of its spring conference in Gateshead yesterday with a promise to turn Ken Livingstone into Ken Leaving-soon in 48 days. For a party hungry for power, the real prospect of winning London is something to savour.

In public, Tory MPs and grassroots representatives insist the party is finally on course to kick out a discredited Labour government which has run out of steam, ideas and money. The momentum is with David Cameron, say the Tories, not Gordon Brown.

But away from prying media eyes, Tory conversations are different. The big question surfaces: why are we not doing better? The nine-point lead they enjoyed over Labour at the turn of the year has dropped to six, according to The Independent's "poll of polls." That is not momentum.

A candid shadow minister admitted: "The voters don't love Brown but they don't want to kick him out and they don't love us. We haven't persuaded them we are a credible government-in-waiting."

The polls reflect trench warfare in which the two main parties scrabble over an ever shrinking slice of centre-ground territory. An unstated aim of the Budget was to deny the Tories space in the hope of pushing them to the right.

Last October, Alistair Darling rushed out proposals to match Tory plans on inheritance tax and "non-domicile" foreign residents. On Wednesday, the Chancellor filched their big money-saving idea by announcing that the 2.6 million sick and disabled people on incapacity benefit (as well as new claimants) will undergo a fit-for-work test. As Chancellor, Mr Brown was cool when this was recommended in a government-commissioned report by the investment banker David Freud. The Tories embraced it and paraded Mr Freud at a press conference. Now – surprise, surprise – Labour has signed up to his blueprint and the popular Mr Freud is an adviser to James Purnell, the Work and Pensions Secretary.

When the Tories claim they can spend more in areas such as health by cutting the welfare budget, Labour will reply: "We're doing that already."

By denying the Tories room to breathe, Brown allies hope voters will regard Labour as more in tune with the challenge of the times – to extend opportunity, the theme which will run through his forward policy agenda as the Prime Minister tries to "own the future". But he will face stiff competition from Mr Cameron who, on the face of it, may look more like the future than a politician who has been in power for 12 or 13 years by the general election.

Labour will portray Mr Cameron as out of touch with ordinary voters – a charge he tried to head off by allowing ITV News to film his family at their home in Notting Hill this week. Yet the Tory leader was more in tune with the public mood than Mr Brown when the row over MPs' expenses blew up. Mr Brown has long acknowledged the gulf between politicians and public but didn't see MPs' expenses as part of the problem.

The policy differences between the big two main parties get smaller. The Tories have matched Labour's spending totals and there is even less chance of them offering tax cuts after Mr Darling announced that the halving of the annual growth in public spending to under 2 per cent will continue for a further two years to 2013. This will anger the Tory right and grass roots. A poll by the ConservativeHome website this week found that 75 per cent of party members want "tax cuts funded by tougher spending controls". No wonder George Osborne, the shadow Chancellor, sounded uncomfortable yesterday when he was asked on BBC Radio 4 how the Tories would be different to Labour. He knows that even if he launched another inheritance tax-style blockbuster now, Mr Brown would probably steal it. "We've got two or three aces, but we won't play them until just before the election," Mr Osborne tells impatient Tories.

One important difference did emerge this week and deserved more attention than it got. Mr Darling's decision to target scarce resources on lifting 250,000 children out of poverty showed that Labour has not abandoned its goal to abolish child poverty by 2020.

The Tories say they share this "aspiration" but don't have any policies to achieve it. Many are uncomfortable with the concept of relative poverty and would rather use any spare cash for tax cuts. Labour has never shouted about a crusade the public has barely noticed but Mr Darling's move suggests this will change. Vive la difference.