There has been something missing for the past seven months, and I have just worked out what it is. It is the sensation of surprise. It was there, very briefly, in the days after 11 May, when it was said on the radio, for example, that the Prime Minister was doing something with Nick Clegg and one wondered why Gordon Brown should be hanging out with the leader of the Liberal Democrats. But it faded fast, and what was striking was how quickly we became used to David Cameron in No 10.
There was a tingle of novelty that lasted for months about the coalition, although that may have been more of a Westminster thing, as there were MPs from two parties on the government side of the Commons chamber. The psychic shape of the House shifted from a two-and-a-half-party system, which had ruled for more than two and a half decades, back to the old binary notation of the 1960s. There is a Government and an Opposition and, for a while at least, a mental pause after Harriet Harman asked her six questions as MPs turned to look for Clegg to ask his two, and then realised that he was sitting, mute, next to the Prime Minister.
That novelty changed to something more threatening in the past few weeks as a large part of Liberal Democrat opinion decided it had been betrayed and its youth wing took to the streets. "But that's the real world for you," as Clegg tells next month's Prospect magazine. And above it all floats Cameron. He has fitted so easily into the role that you might think he had gone to a special school where they train young men to be prime ministers.
In opposition, it was a minor part of Cameron's claim to the top job that he looked the part. But the moment he got the job, his effortless assumption of authority wiped out any doubts about his party's failure to win a majority of seats. Where Gordon Brown, with a stronger constitutional claim, endured three years of carping about the manner by which he came by the office, no surprise attends Cameron's tenure.
Cameron has taken to the business of foreign trips and international summitry as if Eton had role-playing workshops in chatting to Chinese dignitaries. He has turned out to be a pragmatic, pre-Thatcherite Conservative in his dealings with European leaders. He was in Brussels last week, stitching together a "conservative" deal with Angela Merkel and Nicolas Sarkozy to freeze the European Commission budget in real terms. At home, he has shown a sure touch, appearing to be the chairman of a collegiate government – one which has the advantage of delegating the unpopularity of tuition fees to the Liberal Democrats – while stepping in to exercise superior power if issues threaten to get out of hand. Hence the "Cameron takes charge of school sports" stories last week.
It was John Reid, Labour former home secretary, who said last week: "He is a better prime minister than he was leader of the opposition. If he had been as successful as leader of the opposition as he now is as prime minister, and as astute, then the Tories would have an overall majority."
Cameron has two outstanding qualifications for being a successful prime minister. One is that his convictions are adaptable; the other is that he is very polite. He is even more polite than Tony Blair, who deployed courtesy as a political weapon to long and deadly effect. When female Labour MPs ask Cameron questions in the Commons, for instance, he always thanks them for raising a very important subject and agrees with them – sometimes even when they are attacking government policy.
Deadlier still, though, might be Cameron's ideological flexibility. Yes, he's a Conservative, but he welcomed a coalition with a minor party, much of the rhetoric of which has sounded as if it were to the left of Labour, without any public awkwardness. Although in private he sees an expletive-filled "car crash" coming on the detention of terrorist suspects, his temperament remains jovial and he jokes about having more trouble with Kenneth Clarke than with the Lib Dems over civil liberties.
Those qualities of upbringing and temperament, I suspect, will see him through. Polly Toynbee, in The Guardian last week, set out the Labour optimist's scenario: Clegg has destroyed his reputation by tuition fees; Cameron will become unpopular when the cuts bite. She sees a "red carpet of opportunity stretching out" in front of Ed Miliband from here to the election.
Well, she is three-quarters right. Clegg has certainly suffered serious damage, and his party will find it hard to recover even if it replaces him with Chris "Clean Hands" Huhne before the election. And it is also true that the cuts have not started yet. So far, the only public spending cuts to have direct effects have been the reduction in child trust funds and in the small mortgage interest support scheme designed to minimise repossessions. Last quarter the public sector saw a net loss of 33,000 jobs, but that is the result of decisions to pre-empt actual budget cuts next year.
It is the last quarter of Toynbee's "red carpet" thesis that is unconvincing: the idea that when the axe really does fall, the British electorate will turn on the Conservatives, and then turn to Miliband to save them.
Well, it could happen. But we have been here before, after a fashion: a time when a Conservative government had to take painful decisions to put the economy right, and when it was opposed by a Labour Party led by someone whose instincts seemed to be to spend more taxpayers' money. That did not work out well for Neil Kinnock.
Cameron's confidence may eventually be seen as arrogance; his good manners as entitlement. But the effortlessness with which he plays the part of the national leader, just above and to the right of party politics, should not be discounted. It is possible that Toynbee's red carpet is being rolled out for him.