The Tories are turning off undecided voters

Some voters who prefer Cameron to Miliband but Labour to the Tories are starting to make their minds up – in favour of Labour

David Cameron reads a book to Lucy Howarth (6) during a visit to Sacred Heart RC primary school in Westhoughton near Bolton, northern England

If Labour want this election to be about values, the Tories want voters to think above all about who they would rather see in Downing Street. It is easy to see why. Throughout the last parliament my polling found a chunk of the electorate leaning towards Labour but who also thought David Cameron was the best available prime minister.

Conservatives have long hoped Ed Miliband would crumble in the intensity of the campaign, and that the prospect of seeing him in Downing Street would ultimately prove an insurmountable obstacle for many who would otherwise vote Labour.

Yet far from crumbling, Miliband has shown a good deal of resilience in the face of some rather unseemly attacks.

This is one of the reasons why, though most still think Cameron would do a better job, Miliband’s personal ratings have on some measures actually improved over the course of the campaign.

But I think there are other forces at work. Some voters who prefer Cameron to Miliband but Labour to the Tories are starting to make their minds up – in favour of Labour.

To resolve their cognitive dissonance they have to reconcile themselves to the choice of prime minister their vote implies; we are starting to hear people say in focus groups that Miliband has done better than they expected, or that at least he won’t be running the country all by himself.

If the Tories were expecting the contrast between Cameron and Miliband to work as a kind of secret weapon, they are still waiting for it to take effect. They have now broadened their attack to include the SNP, hoping that if the prospect of Miliband himself is not enough to put people off, the spectre of the Scots calling his shots will push some uncertain voters back to the Tories. There is still room for a late swing to the Conservatives, of course, but if undecided voters make up their mind to stick with the Tories, I suspect they will do so very late.

And, crucially, it will be the number of seats each party wins, rather than the national vote share, that will determine who gets to form the next government. It is sometimes observed that Labour are doing better in the crucial marginals than they are nationally, but the picture is more complicated than that.

Comparing my local snap shots with national polling at the time they were taken shows the Conservatives holding on to more seats overall against Labour than they would with a uniform national swing, but failing to gain seats that they would otherwise win from the Lib Dems.

At the same time, my polling has Labour winning fewer Tory and Lib Dem seats overall, and losing more to the SNP, than the national polls suggest ought to be the case. It is, in fact, the Lib Dems who are doing best in the marginals, holding on to more seats against Labour and (particularly) the Conservatives than they would with a uniform swing.

As I always stress, these are not predictions. But one notable finding from my research during the campaign is that Labour seem to be winning the ground war. Though there is no clear relationship between the level of campaign activity and the parties’ vote shares, in Tory-Labour marginals people are more likely to say they have had literature, direct mail, phone calls or doorstep visits from Labour than from the Conservatives.

It would be unfair to think of this as a failure of the Tory campaign and its organisers. As Donald Rumsfeld observed, you go to war with the army you have. If the blue army is being outgunned that is not a matter of logistics, but because it lacks recruits. And that would not be surprising for a party that has been unable to reach very far beyond its core support for more than 20 years.

Also, it is not just the number of people knocking on doors that matters, but what they have to say when the doors are opened.

Some who see the Tory message as rather narrow and negative are inclined to blame its architect, Lynton Crosby. But isn’t this also unfair? Lynton is a professional, brought in to achieve the best result he can with the material at his disposal. Has he not brought discipline, organisation and consistency?

You can quibble with the balance of themes he has chosen – as I have noted more than once before. There has been too much emphasis from the Tories on the opposing leader’s weaknesses (or, in this case, the deals he may or may not do to get himself into office), which suggests to voters a party that can’t have much to say for itself. But if after five years in government the Conservative Party’s policy advantage is confined to the economy and the public finances – crucial areas, but not, as far as voters are concerned, everything – that is hardly the fault of an Australian consultant.

Rather than relying on the identity of their leader and the risks of change, the Tories over the last five years ought to have laid the foundations for a campaign in which they could talk confidently about their plans for public services, and to describe a Conservative vision of opportunity and prosperity for all. Such a message, incidentally, would also find more people ready to go into the streets and deliver it.