That's coalition government for you, they will say. You have to negotiate with your partners. Sometimes that means that cherished policies are ditched. People will have to understand that this too is part of the "new politics" of negotiation and compromise.
However, this can not work to explain a policy that both partners have ruled out.
So today's Guardian front-page report that civil servants have drawn up proposals to target middle-class child benefit is surely one that will be sent back to the drawing board by both yellow and blue ministers.
We had Nick Clegg telling Jeremy Paxman on April 12th that child benefit would not be means-tested:
"We are not putting child benefit into question. I never have and he hasn't either", referring to himself and Cable, and excusing Cable's reference to means-testing child benefit in the Chancellor's debate as a simple verbal slip.
This wasn't true as history, given the Clegg and Cable public u-turns on the issue, but it could not have been a clearer statement of LibDem policy.
And we had Phillip Hammond for the Conservatives on April 27th telling Newsnight that the Tories had ruled out means-testing, even if the LibDem commitment to do so seemed wobbly:
We have made a decision to rule out means testing child benefit because it is a universal benefit. Talking to people, one of the things they appreciate about child benefit that it is universal and easily understood. To start to means test it would erode it ... It reassures them about the availability of the benefit. If you start means testing it, if you start slicing away at that universality, then people are going to ask where you are going to stop".
The lesson is that you can trade away a manifesto promise to your coalition partners.
But coalition can't be used as an excuse to break a promise that you have both made.
Or can it?
PS: Richard Exell on Left Foot Forward notes that Steve Webb will want to persuade his collagues (again) of the argument. So I do hope one of the most progressive LibDem ministers isn't faced with a resignation dilemma so early on.
Much the same could be said of VAT.
The New Statesman highlights the LibDem election campaign poster against a Tory VAT bombshell as one which may rebound, given widespread speculation of a VAT increase.
But perhaps the Business Secretary should take some comfort from what right-wing media outlets were saying as the campaign began? The Telegraph and ConservativeHome suggested the Tories had made "a significant commitment" in stating that their plans did not include an increase VAT.
If you know your history, you might doubt that. So Next Left thought the classic Geoffrey Howe VAT dodge was back in play.
Let's see who was right - and whether it will be an Osborne-Cable two-handed u-turn on VAT this time.