Never mind its readers, the Sun's effect on other media outlets is all-pervasive, and losing its support is disastrous for Gordon Brown
'Nobody,' wrote Trevor Kavanagh, associate editor, 'can accuse the Sun of a rush to judgment.' No, indeed. According to Wednesday's paper, announcing 'we're feeling blue', Labour failed on schools, law and order, health, immigration and, 'most disgracefully of all', supporting our boys in Iraq and Afghanistan.
Labour spent billions on welfare and useless public-sector managers, a 'mind-boggling and tragic' waste, the Sun went on. In its 'ruthless and relentless self-promotion', it told lie after lie. And the 'puerile feud' between Tony Blair and Gordon Brown often paralysed the country.
If it has been as bad as that, one might ask why the Sun took so long to notice. The answer is that the Murdochs (Rupert and his son James) and their papers like to be close to power, and power is visibly draining from Labour.
Governments tend to give scoops to papers that support them, particularly if the support is conditional as it always was with the Sun, but not the Mirror. More importantly, the Murdochs want, and get, favours from government.
What worries them now is the media regulator Ofcom, which has demanded that BSkyB offer film and TV channels to other providers at lower prices, and the BBC, which, with its free news website, poses the main threat to their plans to charge for online newspaper content.
Murdoch senior has never cared for the current Tory leader, partly because David Cameron is an old Etonian and Rupe likes to present himself as a man of the people, partly because Cameron is less Eurosceptic than his three predecessors. But now Cameron has indicated his government would scale down the BBC and restrain, perhaps abolish, Ofcom.
The Sun, particularly in the past 18 months, has been a Labour paper only in the sense that China's current leaders are Marxist-Leninists. Its formal endorsement of Cameron was only a matter of time – and the call to Brown was made by Rebekah Brooks, the former Sun editor who last month took up the post of News International chief executive.
Does it matter? Academics find, to quote one professor, 'zero evidence' of any paper influencing voting habits. But that just shows academics don't get out much. Politicians take a different view.
Alastair Campbell writes in his diaries that the Sun's backing for Blair was 'the fruit of three years' hard work'. Piers Morgan, the former Daily Mirror editor, recorded '22 lunches, 6 dinners, 6 interviews, 24 further ... chats over tea and biscuits, and numerous phone calls' with Blair. Tony Woodley, leader of Unite, tore up a copy of the Sun on the Brighton conference podium last week.
Setting the agenda
If nothing else, seeing negative comments about yourself in the papers each morning, and knowing several million readers are sharing them, is bad for morale.
Newspapers' circulations may have declined – the Sun's is down from well over 4m when it launched its celebrated demolition of Neil Kinnock in 1992 to barely 3m now – but they still set the agenda for TV, radio and the blogosphere, as we saw last week.
Nobody cares much what editorials say, but the daily presentation of politics in news columns and features determines the questions broadcasters ask, the debating points in blogs, the coffee machine conversations and, directly or indirectly, broader public perceptions.
As the French sociologist Gabriel Tarde observed in 1898, 'every morning the papers give their publics the conversations of the day'. In Britain, where there is little partisan agenda-setting in other media, newspapers matter more than ever, as communities splinter, family and class commitments weaken, and politicians are judged as much on personality as policy.
It is not the loss of support from the Sun's leader writers that will worry Brown; rather the knowledge that, from now until the general election, he will be denounced, mocked and pilloried relentlessly and that the cumulative effect, magnified through other media outlets, will highlight his weaknesses to the point where defeat seems inevitable.
He hoped last week would see the beginning of a comeback; thanks to the Sun, it will probably prove the moment when recovery became impossible.