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The intervention of former NHS boss Sir David Nicholson has certainly electrified the election campaign debate about the future of the NHS.

His comments in interviews with my colleague Jane Dreaper and on the Today programme were considered, not in any way off the cuff - and he was probably speaking out with the encouragement of former colleagues in NHS management.

Sir David, former head of NHS England, has a two-fold message on the state of the health service's finances.

In the short term, he says there is a hole in the NHS budget in England which will become clear later this year.

Longer term he argues that more money and sooner is needed than the £8bn extra a year above inflation by 2020 requested by his successor Simon Stevens.

What's more, he says nothing comparable to the £22bn efficiency savings implicit in the NHS England plan has been achieved by any other healthcare system - though he doesn't say its impossible.

Sir David's broader point is that the scale of the task ahead for the NHS in England needs consensus across the political system.

The NHS needs to know there is support for the radical changes implicit in its Five Year View published last autumn.

He argues that the political parties have so far skirted around the immediate financial challenge and have failed to recognise that the £8bn by 2020 is needed for day-to-day running costs, rather than available to fulfil new political pledges.

In government - or, to be precise, political spokespeople who have moved from Whitehall out onto the campaign trail - there is irritation at the suggestion that the NHS might need even more money that it asked for.

As one source put it, Simon Stevens asked for £2bn for 2015/16 and got it in the Autumn Statement.

He said £8bn a year more was needed by 2020 and the Conservatives and Lib Dems have signed up to that.

Yet now - if Sir David is to be believed - that new money is inadequate.

Labour has not made a commitment to the £8bn by 2020, arguing that its promise of £2.5bn a year extra starting from 2016 is the only one fully funded by identified tax measures.

This week there have been signs that Labour is putting the Five Year View at arms length with a comment from Andy Burnham that it left "big unanswered questions".

The Greens and the National Health Action party have both said billions of pounds more than has been offered by the major parties is needed by the NHS.

They argue the other parties are in denial about the scale of the financial challenge and will no doubt feel that the Nicholson comments endorse their funding plans for the health service.

UKIP has pledged £3bn a year more for the NHS.

If the Nicholson intervention does one thing it is to serve as a reminder that whatever the political arguments before polling day there are some really tough decisions to be made by the new administration.

Governments tend to make the least popular choices early in a parliament.

Working out how much the NHS really needs, and whether tax rises will be needed, could be high on that list.