Of course, the Conservatives have changed in their acceptance of a more socially liberal Britain, particularly in trying to diversify the face of the party and be more open to non-white, women and gay candidates, and conceding that they were wrong on issues like section 28. I think this is an important and welcome shift.
But the Conservatives did not - after 1997 - believe that they needed to change their ideas and core beliefs to come back.
After 2005, after three defeats, David Cameron's argument for change was accepted - yet the ambiguity was always about how deep that change would go. In 2006 and 2007, this was an open question, and it was often suggested that arguing that "the Tories haven't changed" would seem churlish and unconvincing.
In the last 12 months, the argument on the right has shifted again. And the David Cameron project, after the recession, no longer challenges his party's Thatcherite instincts on public spending, as it did when he was pledging to stick to Labour spending plans. (And last night we heard Tim Montgomerie argue that the new green Toryism - the highest profile brand decontamination exercise to date - hasn't convinced the party that tackling climate change matters.
There are two problems with this.
Firstly, even if it is rather more convincing to argue that the Tories haven't changed than it might have seemed two years ago, Labour risks this becoming almost 90% of its public argument, and crowding out Labour's positive argument and definition of its own fairness cause and agenda, and argument about what it wants a further term in office for.
Labour does need to define a clear electoral choice between itself and its opponents. But Daniel Finkelstein is convincing on the danger for Labour of talking too much about the Conservatives (and perhaps saying more about itself in the way it does so). Labour can define the Conservatives best by testing it on content, by setting out clear Labour arguments and policies and seeing if modernised Tories accept them or not.
What Labour can do most to define the Conservatives is not to talk about them; it is to be us.
Secondly, note too that it is not only the Labour party which wants to argue that the Tory party hasn't changed. It is also an argument being pushed from the right of the Tory party too - to challenge any sell-out to Fabianista social democracy.
I wrote about Cameron just before he became leader in 2005 for Prospect that the scale of the Cameron project would be an important indicator of New Labour's long-term legacy.
"Long-term political change is embedded when you convert your opponents. If David Cameron makes a serious attempt to modernise the Tories, Labour should welcome it."
In 2007, Cameronism was largely a conservative politics of accomodation, coming to terms with a new Labour settlement, and doing the traditional conservative thing of persuading his party to live with change.
So pointing out that the Tory party remains a largely Thatcherite force is giving Labour a morale-boosting way to rally the troops and take their fight to the country.
But, in the long-run, it also suggests that 12 years of Labour government have done less to shift the centre of political gravity than they should have done.