So what's going on? There are two diametrically opposed accounts of the new Tory wobbles.
Labour's argument is that the Conservatives have changed much less than their image makeover would suggest.
Gordon Brown argued yesterday that cutting inheritance tax while promising an age of austerity and spending cuts, defending hereditary peers in Parliament and promising to bring back fox-hunting doesn't sound like "change".
This morning's Observer editorial offers a more nuanced account - Turn right at your peril, Mr Cameron which notes that the Tory right have made significant advances in most of the internal policy skirmishes - spending and cuts, grammar schools, marrigage and Europe - under Cameron's leadership.
The alternative reading is that the Tories have not been nearly Tory enough.
This view is highly sceptical of the Tories desire to protect the NHS budget while promising to reduce the deficit too, and then seeming to row back sharply on their central cuts message last month.
This is the main message of the Tory "party in the media" and of much of the activist blogosphere too. The ConservativeHome recovey plan unveiled on Friday essentially suggests that the themes of the 2001 and 2005 elections would resonate much more this time around. The main challenge is to the party's failure to bang the drum on immigration.
The right also believes the leadership has spent far too much time on the counter-intuitive theme that Tories care about climate change, particularly since it is now clear that most of their Parliamentary candidates and activists don't think it matters very much, if at all.
The Observer notes the obvious contrast:
With the Tory lead looking brittle, Mr Cameron will come under mounting pressure to appeal to the instincts of his party's restive right-wing activists. But too much deference in that direction has been a major source of his problems. It cannot also be a solution
But it may be that a third possibility is the most plausible explanation. It has been the Conservative attempt to square this circle has led to a diverse and contradictory set of propositions which has left everybody unsure as to what the party stands for.
As Alex Massie points out on the Coffee House blog, the Conservatives this weekend have unveiled six pledges for their election campaign which capture the apparent incoherence of their overall message:
what we have here is a) a pledge to act on the deficit that is accompanied by b) tax cuts and c) a raft of commitments to increased spending.
The Conservative approach has been to embrace the contradictions, with a "trust Dave" message.
So they began the year planning a Presidential campaign, for a candidate and not a party. They retreated in the face of effective mockery - but will effectively return to that theme again today.
However, the almost exclusive focus on Cameron has risked turning an electoral asset into a liability. Cameron's personal ratings have dropped sharply as concerns about depth and authenticity are brought to the fore. Perhaps more significantly, the Tory campaign seems to accept the validity of the central challenge to the party. If David Cameron is the only "change" message that the Conservatives have, then the "have they changed?" challenge becomes stronger.
However, the tendency for campaign analysis focus on leaders, personalities and tactics risks obscuring that broader choices on political strategy and plans for government is probably the main reason that the election battle appears to be tightening.
The central strategic ambiguity about the Cameron project has been about how far it is intended to be essentially a conservative exercise in accomodation to the New Labour legacy (as seemed quite plausible reading from 2005-7) and a recognition that the centre-ground did shift in a social democratic direction, or whether the "brand decontamination" was intended to make possible a significant if gradual rightwards shift couched in more compassionate language.
In response to the economic crisis, the Conservatives found their voice most strongly on the issue of deficits and cuts. They retain a recognition of increased social liberalism - which makes it necessary to choose a more diverse group of candidates - but the idea that the primary test of a Conservative approach is that it seeks to reduce the size of the state has been strengthened.
Over the last decade, Labour won a public argument to put investment in public services ahead of tax cuts, in a debate essentially framed about how to spend the proceeds of growth. The Cameron leadership essentially wanted to concede that argument after three defeats; their activists and right-wing commentators did not. This debate over Labour's spending plans was the most important internal debate inside the party until 2008. Eventually, the leadership changed its position.
The context has changed. That the need for some "cuts" has become common ground between the major parties, leads many Conservatives to assume they must automatically have won the argument about public spending - and so to forget the core message of their successive defeats, leaving them with no way to understand why the public appears sceptical of their message.
A politics of the surplus has been replaced with the politics of the deficit. Yet this does not obscure choices about how they are made, where they fall, and about the balance between spending, tax, the speed of deficit reduction and the role of growth. In fact, the different instincts between the parties become more and not less important.
John Rentoul writes today in a "policies smash personalities" column for the Independent on Sunday:
The big-picture reason is probably that people are more worried about jobs, schools and the NHS than they are about the deficit ... I think the NHS and schools are another example of the disconnect between media and mass opinion. Despite being told by the media that hospitals kill people and schools make them pregnant, most people know that their NHS and their schools are better than they were a decade ago, when public spending started to rise. They still associate the Tories, despite four years of detoxification, with underfunded public services.
This helps to explain why the Conservatives, this month, considerably softened their language about spending cuts, before explaining that nothing substantive in their position had changed.
Yet every attempt to explain the position appears to leave it less clear than before.
So there will be renewed calls from every quarter for the Conservatives to clarify what they stand for before the election campaign begins. Perhaps the only thing that can be said with confidence is that they are very unlikely to do so in any substantive way, instead heralding more (contradictory) micro-announcements as adding up to the core message of 'change'.
The assumption has always been that less is more. What looks shakier is the long-held confidence that this would be enough. But it is almost certainly too late to change course significantly now.