As part of the interesting 'maths' in their manifesto, the Tories have committed to £12 billion more cuts in benefit payments over the next parliament.
In interview after interview MPs and ministers have consistently refused to say where these cuts will come from, including multiple times to the BBC's Andrew Neil on The Daily Politics ever since the promise was made.
As Neil pointed out, a refusal to provide the detail can only mean either they don't know where the axe will fall - and the £12 billion is a figment of their imagination - or they will not say - and they are keeping vital information from the voters.
A pretty low tactic, but more likely to be successful than blurting out the alternative.
Only one man appears not to have read the memo, one of the most dismal cabinet ministers in recent government history.
Step forward Iain Duncan Smith, who faced with the question on The Daily Politics stated that his government simply hadn't "done the work" on this issue despite making it a key part of their offer to the electorate.
When asked again about where the cuts would be made, Smith said:
"As soon as we have done the work and had it properly modelled then we will let everybody know what that is."
This apparently frank confession would be embarrassing at the best of times, suggesting the Conservative Party set out their manifesto without ever working out how key parts would be funded.
If this was the end of the story, there would be a few days of Tory red faces (florid complexions go well with the punishing spirit) at Smith's incompetence and the Tory election machine would roll on.
But another story reported in yesterday's Guardian shows he may have directly misled voters.
A document has been leaked from within Smith's own Department for Work and Pensions which showed that last year civil servants, presumably under the direction of politicians, secretly developed a range of benefit cut options in response to the government's policy to cap the overall welfare bill.
It is inconceivable that these options weren't shared with Smith as the minister in charge of the department, given that it was a key policy of his, and inconceivable that these options weren't discussed when the Tory manifesto was being developed at the same time.
It appears that the party preferred to hide the cuts rather than face the judgement they would inevitably have brought.
Going through some of them it is easy to see why they would be hidden away.
The government has spent a huge amount of effort developing a 'moral' basis for their previous cuts, talking of 'strivers versus skivers' and of people 'sleeping off a life on benefits', while putting forward endless policies that assume unemployed people are workshy and need to be forced to take jobs when the vast majority only want to work.
The list of potential cuts stands as an acknowledgement that, despite this stance, in reality the size of the benefit bill and the fact that only a tiny proportion of it supports unemployed people means they will need to breach this public moral stance if they are to make the cuts they have promised.
The leaked document shows who will suffer as a result - children, through child benefit cuts, the working, through tax credit cuts, employers, through taking more money from them to pay for maternity pay, and the sick, through cuts to their support.
None of these groups fits into the narrative of dishonesty the Conservatives have been so desperate to propagate, and it is no wonder that Smith decided it was preferrable to pretend he was clueless rather than cruel.
Those who have watched his department operate over the last five years know the truth.
He is both.Suggest a correction