Like many commentators, I got the general election wrong. I thought Labour would finish narrowly behind the Conservatives but would form a government. Unlike most commentators, I feel a responsibility to admit this mistake in the public square. And I want to discuss why so many of us were mistaken this time.

There seems precious little chance of this generally. Too many commentators on the right have spent the last week in hero-worship mode towards David Cameron and, in particular, George Osborne. Meanwhile, way too many on the left have equally rapidly immersed themselves in a ridiculously premature Labour leadership election that provides a handy duvet beneath which to hide from electoral and political reality.

It is a mere eight days since Ladbrokes were offering 10-1 odds against a Conservative majority government

I know that we live in a what’s-new media environment that has no time for yesterday’s stories. I know that it is in the nature of journalism to always surf whatever passing wave comes along.And I know that lots of readers, like lots of writers, also prefer the warm bath of the familiar to the cold shock of the difficult and new. But it is pathetic for those who were surprised at the outcome of the election a week ago to act as if nothing much has happened – when it manifestly has. It is a mere eight days since Ladbrokes was offering 10-1 odds against the Conservative majority government that was convincingly elected less than 48 hours later. It is just over a week since we gathered round the TV screens at 10pm on election night, entirely confident that Britain would have a hung parliament.

Today, it feels as if large swaths of the population are in complete denial that such moments really existed. It is as if the facts are too difficult to contemplate. Yet today the Conservative party has 99 more seats and 2 million more votes than Labour. Last week Labour polled under 10 million for the third successive election, having only done so once before (1983) in the postwar years. Meanwhile in Scotland, there has been a cultural revolution. Why?

The easy bit is to blame the polls, although they were right about Scotland and the Lib Dems. In most elections of my lifetime the polls have been broadly correct, and one could have confidence in them. But in 2015, the polls have been a humiliating disaster, even more so than in 1992. It will take years for the pollsters’ reputations to recover, and rightly so.

But it’s not just that the wrongness that matters. It’s that, in calling it all so wrong for so long, they consistently produced results that shaped the way that all the parties prioritised and campaigned and all the media reported. At least as long ago as last autumn, every main party, from the Tories and Labour to the SNP and the DUP, was preparing for a hung parliament that still seemed certain at 9.59pm on 7 May. The polls should reflect the politics. Instead the politics reflected the polls.

Yet it is also a mistake to seek easy refuge in the idea of a late swing to the Conservatives that the opinion polls were unable to spot. Clearly, some people went into the polling booths anddecided at the last minute to vote Tory. As ever, after the event, there is now a lot of anecdotal evidence to that effect. But it is not enough to account for the substantial 3%-4% swing in the Tories’ favour in the less than 24 hours between the final polls and the actual results.

That discrepancy can only be satisfactorily explained by accepting that the polls have consistently understated support for the Conservatives while consistently overstating support for Labour. This phenomenon goes back years and affects even the exit polls, as it did once again last week – the Tories won 15 more seats than the exit poll predicted. The same thing happened in 1997, when Tony Blair’s Labour polled 47% in the BBC exit poll and 44% in the country, while John Major’s Tories polled 29% in the exit poll and 31% in the country. To describe this as the “shy Tory” phenomenon is simplistic and unfair to shy people. The reality is surely that when forced to make their decision, significantly more people give priority to the arguments that the Tories are making than to those made by Labour.

The left should remember Oliver Cromwell: ‘Think it possible you may be mistaken'

If Lord Ashcroft’s post-vote poll is to be believed – which, in the light of events, perhaps it cannot, but read on all the same – there were two equally powerful reasons people voted Tory last week. One was the party leader – 71% of Tory voters thought Cameron would make the best PM, while 39% of Labour voters thought the same about Miliband. But the other was what the Tories believed – the same proportion of Tory voters, 71%, trusted the party’s “motives and values”. All other reasons for voting Tory paled beside these two.

Translate that into real human beings who vote, and you have something that deserves attention. It is also something that many on the left cannot get their heads around and do not try to either. They should remember Oliver Cromwell: “Think it possible you may be mistaken.”

Most Tory voters, the poll says, trust Tory motives and values. Think about this. Think about it hard. On the left, Tory motives and values are often stereotyped (as Labour motives and values are, of course, caricatured on the right) in ways that make people on the left feel good about themselves. The Tories in this view are variously greedy, mean, destructive, selfish, uncaring, small-minded, racist, nationalistic and more. But what if the motives and values that Tory voters see are less extreme – things like competent, reliable, realistic, prudent, generous, tolerant, decent or patriotic? None of those qualities is in itself in any way objectionable. It would be reasonable to vote for a party that you thought had such qualities – and I suspect lots of people did on 7 May.

There are many reasons the Tories won the 2015 election and Labour didn’t. But the search for understanding requires us to look at what was attractive about the Tories, not just what was unattractive about Labour. A lot of people continue to be naive about this. They sit in a bubble in which they see what they want to see and hear what they want to hear. As a result they get things badly wrong and are surprised by their mistakes, which they then shrug off. Some humility, some honesty and some open-mindedness are urgently in order. Of course, ask why Labour failed. It’s an important question. But ask at the same time why the Tories succeeded. If anything, that’s even more important.