Conventional wisdom has it that political parties win power by promising to cut and not raise our taxes.
But, as we report today, Labour is now gambling that there is one exception to this: the NHS.
It is examining how it can go into the next election promising to increase funding to the health service at a time when public finances will be no less tight than they have been for the past five years.
To do so the party realises it will almost certainly have to ask us to pay more and hope that we care more about our future health than our current tax bill.
Rationally, we should accept this. New technology and a growing elderly population mean that, unfortunately, the proportion of our national income we spend on health must rise and the money has to come from somewhere.
So far, most of the savings that have allowed the NHS to get through the past four years (of broadly flat spending) have been one-offs and are nearly exhausted.
Most health experts agree that we are now at a tipping point where "doing more for less" in the NHS is no longer sustainable.
No extra money will mean longer waiting times for cancer treatments (a form of rationing), not spending money on the latest drugs and the closure of smaller hospitals.
But we are not always rational. People convince themselves that fabled "efficiency savings" can be found and that if we could eliminate "waste" then the NHS would be fine and we can keep our money.
The truth is that the NHS needs more money and efficiency savings if it is to keep up with our understandably high expectations of it.
Labour, to its credit, has recognised that and so, privately, do many Conservatives. But it is a hard message to sell to voters. What's good for our health will be bad for our wallet.