Some on the left, though, believe the Tories have had no option but to use such negative campaigning. Phil says:
When your coming manifesto promises little more than demented and unnecessary cuts, a possible EU exit, and precious little else the Tories have already lost the politics.
This poses the question: what might a more positive Tory platform look like? If I were Cameron, I'd stress three elements.
First, I'd make more of a virtue of smaller government. I'd claim that this isn't merely a byproduct of austerity, but an end in itself. For example, I'd point out that cuts can increase government productivity: the ONS estimates that the output of government services has risen despite lower manpower. I'd also argue that smaller government can increase growth, perhaps - in the longer-run - by fostering a culture of self-reliance.
One element of this should be greater civil liberties: if you're going to cut police numbers, you must give the remaining coppers less to do. Here, the coalition has missed a trick. Many of us resent the increase in criminal offences under New Labour. Rather than reverse this, however, the government has continued the trend.
Secondly, I'd revive interest in happiness policy and the Big Society: the two are related, because strong social networks improve well-being. In this context, the promise to give paid leave to do voluntary work is a good idea. But rather than offer it as a gimmick, it should be part of a narrative; volunteering improves well-being and might even have an economic payoff too.
Thirdly, I'd adopt the "blue-collar conservatism" of Ruth Davidson of Robert Halfon, which directly addresses questions of workers' living standards. This might include tax credits for firms that pay living wages and, as Mr Halfon, has suggested, greater support for trades unions. These are the "little platoons" of which Edmund Burke approved, and can be a more efficient alternative to unwieldy and inflexible labour laws. It could also include tax breaks to encourage worker ownership: "popular capitalism" is a feasible Tory slogan.
All this would, I reckon, help defuse Labour's strengths - that the Tories are the the "nasty party" on the side of the rich. It would give substance to Danny Finkelstein's claim this week that Labour doesn't have a monopoly on decency.
Of course, many of you will claim - with reason - that such an agenda has its faults. But it is surely more coherent than mere prating about the nation's credit card, and more attractive than personal attacks.
So, why aren't we hearing more about it?
One possibility is just incompetence: the Tories have imported Lynton Crosby's negative campaigning tactics from Australia without considering whether they will work here. Another possibility, though, is structural.Perhaps the Tories have been so captured by plutocrats and big-staters that they have forgotten that there could be a decent conservatism.