By Brian Wheeler
Political reporter, BBC News
The extraordinary outpouring of online support for the NHS in the past few days has proved beyond doubt the power of micro-blogging site Twitter to shape political debate in the UK.
Daniel Hannan is a longstanding critic of the NHS
But it has also demonstrated a far older truth about British politics - that you criticise the health service at your peril.
Labour-supporting actor Stephen Fry, who probably did more than anybody to spread the Tweeting craze in the UK, must have thought he had summed up this sentiment perfectly when he tweeted on Wednesday: "Know this, Republicans. Even the most right wing British politician wouldn't think of dismantling our health service."
But he had not reckoned with Daniel Hannan, the Tory MEP who has become an unlikely darling of US television news talk shows, where he has been able to confirm all of the worst suspicions Republican-supporting opponents of Barack Obama's reforms have about Britain's "socialised" health service.
Mr Hannan knew his comments would provoke outrage from Labour politicians - the only surprise was that it took so long for it to happen.
Mr Hannan wrote on his Daily Telegraph blog before the furore reached its current fever pitch: "When I was in Washington last week, I joked that, within minutes of my speech, John Prescott would be accusing me of "insulting our hard-working doctors and nurses". I over-estimated the old bruiser: it took him a week.
"The idea that I - or anyone else - would set out to offend 1.4 million NHS workers needs only to be stated to see how silly it is. You see how the Left works, though. Any suggestion that the NHS might be improved upon is shouted down as an attack on the people in it - which is precisely the point I was making about how hard it is to reform so large a bureaucracy."
Health Secretary Andy Burnham has even accused Mr Hannan of being "unpatriotic" for daring to "slag off" a British national institution in the "foreign media".
Former Deputy Prime Minister John Prescott has recorded a video message to the American people defending the NHS and accusing Mr Hannan of "misrepresentation".
But the MEP's comments have also touched a raw nerve with the Tory leadership, who have done so much in recent years to portray the party as a true friend of the NHS.
Conservative leader David Cameron has had to go into full damage limitation mode - dismissing Mr Hannan as a man with "eccentric views about some things".
Like Prime Minister Gordon Brown, whose sight was saved by NHS doctors, Mr Cameron has very personal reasons to be grateful to the health service.
Mr Cameron said his family were 'grateful' to the NHS
His profoundly disabled son Ivan, who died earlier this year, needed round-the-clock care, much of it provided by NHS staff.
Witnessing the dedication of health service doctors and nurses at first hand is said to have transformed Mr Cameron's attitude to public servants in general and made him a determined champion of the NHS.
As an MEP, Daniel Hannan has no responsibility for health policy - and he does not pretend to speak for the Tory leadership on it or any other issue. Labour's talk of him being a "leading Conservative" is somewhat overblown.
But he probably does speak for a wing of the party who feel disenfranchised by Mr Cameron's brand of "progressive" Conservatism.
His coruscating demolition of Gordon Brown in the European Parliament earlier this year, when he told the prime minister to his face that he was a "devalued" leader of a "devalued" government, became a worldwide hit on YouTube and brought him to the attention of the US TV networks.
But it also won him a following among grassroots Tories, who successfully campaigned for him to be allowed to speak from the platform at this year's Conservative spring forum, where he gave a typically robust defence of British liberty against the EU "superstate".
Nervous party bosses were said to have asked for approval of the text beforehand.
Mr Hannan is also a longstanding critic of the NHS, arguing in a book he co-authored with another Tory maverick, Harwich MP Douglas Carswell, that it should be replaced by a Singapore-style system of "personal health accounts".
And judging from the comments on the Conservative website, there are plenty in the party who share his concern about health spending and the fact that David Cameron has pledged to protect it from future cuts.
"Despite the huge amount of money which has been thrown at the NHS our hospital system is still sick and likely to remain that way until such time as we start making this money work for us," says one.
But others also relate heartfelt tales of NHS staff saving the lives of their children - illustrating the difficulty any politician comes up against when talking about the health service.
It is impossible to divorce it from emotion - particularly when patriotism is thrown into the mix.
And with both main parties retreating into ever more entrenched positions the chances of having a serious debate on the issues are receding by the second.