Tory Phillip Hammond (NB not George Osborne) has just been on BBC News 24 skating around questions regarding the Tory promise to "recognise marriage in the tax system". They will soon announce what form it will take. But it is clear the Conservatives are going to encounter some significant problems between the moral appeal of the policy to their natural constituency on the one hand, and the social justice appeal by which they have sold it, on the other. They are caught between a rock and a hard place, and their love affair with the policy may soon be "on the rocks" as a result.
Jonathan Isaby at Conservative Home reckons it will be the "centrepiece" of the Tory campaign .
The immediate difficulty of course is the cost implications, at a time when everyone is seeking to promise spending cuts or higher taxes. This may mean that the proposals, when they emerge, will be watered down.
Tim Montgomerie's conservative estimate  is that a full transferable tax allowance for all married couples (including civil partners) would cost over £3bn but a transferable tax allowance for married couples with children under three years old would cost just £600m, for example.
There are a variety of options for 'honouring' the pledge. Simply reintroducing a transferable version of the old Married Couple's Allowance is probably not what will be proposed. It might be that it only covers new marriages, or an element will be introduced to the Tax Credits system which is linked to poorer families. It may even be on a progressive basis (ie the longer you are married, the more tax break you get). We’ll have to wait and see what emerges.
But the crucial point is something different. It is the difference between who it appeals to on the one hand, and how it is being sold on the other.
There is little doubt the primary appeal is to grassroots Tories and Daily Mail readers because it appears traditionalist and 'moral'. But it is being sold to others on the basis of 'social justice'. Indeed, much of the Tory social policy seems to revolve around trying to socially engineer stable families. 'Broken' families are seen as at the root of 'Broken Britain.' The push on this has come of from Iain Duncan Smith's Centre for Social Justice.
But this means there is another major problem to the financial one, and that is whether there is no recognition for civil partnerships. If not, it will immediately open them up to further charges of homophobia, following Chris Grayling’s comments about Bed and Breakfast owners refusing hospitality to gay couples . Their sensitivity to the issue was evident today in Cameron dropping the "gay or straight" line  from his election campaign launch speech in London. It seems too that Cameron's support from LGBT people is falling .
But neither can the Tories really claim that their social policy doesn't apply to gay couples, as they sometimes have children too. The breakdown of a civil partnership, presumably according to their own logic, must have the same detrimental effect. But if the policy does cover gay couples, it will not make some Daily Mail readers and Tory grassroots particularly happy - particularly those upset about a moral equivalence between civil partnerships and marriage.
The Tories may have 'unequally yoked' themselves to a particularly unhelpful policy.