The Stupid Party's learnt a new trick - to pretend that hand-outs to its supporters are a way of helping the worst off and benefiting society.
The family is the most important institution in Britain and that if we are serious about tackling the causes of poverty and social breakdown then we must look at ways of supporting families.
Now, it's certainly true that people from broken homes are more likely to become criminals or poor in adulthood, and less likely to finish education, as this report describes.
But it doesn't follow that these problems will be diminished by financial incentives for families to stay married.
Incentives matter at the margin. They'll only encourage the marginally dysfunctional family to stay together - the Ruth and David Archer type. But these generally aren't the families that produce kids who become poor or criminal adults. The families that do this tend to be deeply dysfunctional, who either won't respond to tax incentives to stay together, or won't benefit if they do stick together; my mum and I were delighted when my dad left home (when I was around seven), and I'm certain my life would have been worse had he stayed.
If we're being generous, we can say that Cameron is committing a version of the representativeness fallacy here. He thinks that the solution to a problem must resemble its causes - so that if poverty or anti-social behavour is caused by family breakdown, the solution is to stop families breaking up.
But it ain't necessarily so. If a man's been hit by a bus, you don't restore him to health merely by reversing the bus. More cost-effective ways of helping kids from bad homes becoming poor might involve higher welfare benefits, better schools or better adult education. Tax breaks to married couples, by contrast, carry huge deadweight costs; they 'll mostly go to couples who'll stay married anyway, and won't produe dysfunctional children.
If we're being ungenerous, we could say that it's these deadweight costs that Cameron wants. He wants to pander to his supporters, whilst looking caring.