The people who need to get over it, of course, are the headbangers on the Tory right. It's not a surprise that Simon Heffer and Lord Tebbit think Cameron a failure, nor that they believe that a set of policies more closely aligned to their own beliefs would have produced a Tory majority of, what, 20? 40? 100? Maybe they are right but I'm not sure they've presented much evidence to support these conclusions.
Consider these facts:
Cameron's Conservatives won nearly two million more votes than Michael Howard's party managed in 2005. Even if you accept, reasonably, that Labour's record in government ensured they would lose votes it does not follow that those votes could only go to the Tories.
Secondly, Cameron won a greater share of the popular vote than Tony Blair managed in 2005.
Thirdly, his margin of victory over Brown, in terms of vote share, was equal to the margin Margaret Thatcher achieved against Jim Callaghan in 1979.
Fourthly, the Tories gained more than 100 seats. Not quite enough, but a lot.
None of those four truths suggest Cameron failed. On the contrary, they suggest that with the system* and the odds stacked against him he came very close to achieving a truly remarkable victory. As it was he has to settle for a good but not quite great result.
So did, as some suggest, UKIP cost the Conservatives victory? Not necessarily. To believe that it did one must assume that no voters would have been turned-off had the Tories made a greater, more obvious play for UKIP (and, alas, BNP) voters. This does not seem a credible proposition. Sure, UKIP may have cost a handful of seats but winning those seats with those votes could have triggered losses elsewhere.
Despite what the malcontents on the right say, immigration was a big part of the campaign and just about the only subject discussed at length in all three leaders debates. Meanwhile, the idea that talking about europe more would help the Conservatives is, at least, a debatable point. There may well be a mild-eurosceptic majority but that doesn't mean voters want to hear the Tories banging on about Brussels all the time. Doing so suggests a certain (well-meaning I'm sure) fanatacism that does not, I hazard, play brilliantly.
Furthermore, look at the map. According to his critics, Cameron would have won if only he had been more right-wing and shown himself a true Conservative. Well, first, Cameron did win in most of Britain. The Tories recovered somewhat in Wales and made great strides across most of England. Indeed, if the election had been an England-only affair the Tories would have a comfortable working majority. This does not suggest that huge numbers of voters were turned off by an excess of moderation.
And look where the Tories fared worst: Scotland and London. In the former Labour's vote actually went up; in the latter the Tories managed only a 2.5% swing. Are people seriously suggesting that in either Scotland or London - combined population more than 10 million people - the Tories failed to make gains because they had abandoned too many "core" Conservative principles? Really?
On the contrary, their struggles in Scotland and London suggest that, albeit for different reasons, the Tories lost seats, or chances of winning seats, because despite all the work that's been done since 2005 voters were not persuaded that the party had really changed.
I assure you that the voters of Stirling and Angus and Galloway were not saying to themselves that they'd have voted Tory if only Dave were more like that nice Michael Howard. And I rather think that the voters of Hampstead, Hammersmith, Tooting and Westminster North would agree with their Scottish counterparts on this. For that matter, would Tebittism have swept the south-west? I have my doubts about that too.
So the parts of the country in which the Tory brand was most toxic remained, on the whole, the parts most resistant to Cameron. It's very strange to hear people arguing that this proves the whole project a futile waste of time and effort and principle. On the contrary, it validates the Cameron approach. He got very close - without losing the suburbs or the shires - but in the end just not quite close enough. Would the Tories have lost seats elsewhere if more voters in London and Scotland had been persuaded that the party really had changed? Perhaps but I'm not convinced they would have.
The old guard may try to blame Cameron but I've yet to see much evidence supporting their claim that the Tories could have won in London (or Scotland!) if they'd followed the advice given so freely by the Tory Taliban. As David Frum says: "Nostalgia cannot substitute for analysis, and assertion is not information." Quite.
*Bigger share of the vote than Blair in 2005 = 50 fewer seats.