THE referendum's month-to-go milestone has been marked by three opinion polls, each of them bringing good news for the Yes campaign.

Two on Sunday and another yesterday all showed the pro-independence camp chipping away at the No side's lead. Panelbase, which has consistently found the highest levels of support for Yes among the various pollsters, put the gap at just four percentage points, excluding don't-knows. That's knife-edge territory. ICM had No 10 points in the lead, four points tighter than a month ago, while YouGov yesterday reported a 14 point gap, down from 22 points.

The three surveys were conducted last week, as First Minister Alex Salmond sought to put Scotland's devolved NHS at the centre of his independence campaign. Having claimed for days that increasing privatisation down south would have knock-on effects for NHS Scotland's budget, he went a step further last Wednesday, pledging to enshrine a publicly-run health service in an independent Scotland's constitution

If Mr Salmond's focus on the NHS is beginning to shift public opinion, the No campaign only has itself to blame. At first, pro-UK MSPs and MPs seemed content to dismiss Mr Salmond's claims as blatantly baseless scaremongering more likely to provoke ridicule than raise concerns. Doesn't everyone know the NHS is Holyrood's responsibility? It all looked like desperate stuff.

In fairness to his critics, Mr Salmond has struggled to draw a convincing connection between privatisation down south and privation in Scotland. That's perhaps because the figures tell the opposite story. Far from privatisation slashing budgets, rising health spending down south is set to boost the Scottish Government's budget by £1.3 billion over the lifetime of the present Westminster Parliament under the effects of the Barnett Formula. Mr Salmond even acknowledged the point during a BBC Radio Scotland interview yesterday, admitting "the consequentials for health have gone up". But he was not to be diverted from his main argument. Scotland's overall budget had been cut by eight per cent, he said, before going to claim, in the face of commitments to the contrary by the UK parties, that patients would face charging in England as part of a privatisation agenda designed to cut costs.

Boiled down, the First Minister's fears seem to be based on the UK Government's present austerity programme and a deep suspicion about its intentions. In that case, the question about NHS Scotland comes down to the biggest referendum conundrum of all for most voters: would an independent Scotland be better or worse off? That, in turn, comes down the SNP's economic plans. Think tanks have suggested an independent Scotland would start life in slightly worse financial shape than the UK and face tougher challenges going forward as the population ages and oil declines. The real question facing voters is this: would Mr Salmond's plan to end austerity, by borrowing big in the early years then making the economy grow by raising productivity and getting more people into work, protect the NHS?