Today the Liberal Democrats announced and eye catching policy to improve NHS funding by £8bn a year by 2020 (in England). This matches the figure asked for by NHS England chief Simon Stevens - so it isn't plucked from thin air.
How is this to be paid for? First £2bn extra is already planned and accepted by the other parties (Labour want to add another £0.5bn). A further £1bn comes from more taxes on the wealthy. The rest will be gradually added as the economy grows. The Lib Dems say that public expenditure should keep pace with national income.
There are good and bad things about this new policy. First the good thing. The £8bn funding figure is entirely credible, given the direction of demographics. Mr Stevens is no lefty. He knows that the NHS can be more efficient and has plans to make it so. But that only gets you so far. Any party that promises to keep the NHS within its current scope and free has to address this gap. This moves, or should move, the debate on the NHS out of the area of gimmicks and into serious choices.
Except that it doesn't. They've made the whole thing look to easy. Tax some other people a bit more and the rest comes from growth. If it's that easy the other parties can do it too. This is not different in substance to what Labour are offering. It is more of a challenge to the Tories who want to use the proceeds of growth to fund tax cuts.
And growth cannot be guaranteed. There are severe economic headwinds, from demographics, from changes to technology, from changes to world trade - to name but three. To say nothing of the legacy of piles of household and state debt.
To be distinctive, the Lib Dems needed to make it look harder. Which in practice means raising taxes - income tax, national insurance or VAT. Remember Paddy Ashdown's promise of 1p income tax for education? This would have made the promise more credible, and got a real debate going. It would then be Labour who would be forced to mutter promises about future growth, which the public are likely to discount.
Instead this looks like another politician's promise that is less than it seems. What a pity.