The Tories’ lead over Labour has been slashed, from around 18pts to less than 10. The last two polls have put it at 5 and 8 points. Surely the election wouldn’t now have been called if Theresa May had foreseen this.

But is the tightening a true reflection of public opinion, or are the polls wrong?

Let’s start with the argument that the polls are misleading. My last two posts have pointed towards that – showing that leadership rating is usually a better guide than voting intent to the gap between Labour and the Tories at the election. My analysis was drawn from Matt Singh’s work and he’s now published a more comprehensive study which came to pretty much the same conclusion I did (not surprisingly since mine was based on one aspect of his), that the Tory margin of victory looks likely to be around 15pts.

The polls could be wrong because they’re no longer being conducted among a representative sample. The Labour manifesto launch might have motivated the more enthusiastic Corbyn supporters to take part in polls, skewing the sample of those who voted Labour in 2015 towards people who’ll vote Labour again now.

Matt’s written a further piece that adds weight to this, suggesting that Labour’s surge in the polls is dependent on people who didn’t vote in 2015 and on younger people. Both are relatively unlikely to vote. This might suggest that the polls are indeed a bad guide to the election result.

This isn’t just a matter of sifting through the polls. One part of Matt’s analysis was from local election results, so was independent of opinion polls.

And there’s another independent set of evidence to support this: reports of focus groups and doorstep conversations. If Labour really had surged, by around 8pts, and the Tories had dropped off by a couple of points, I would expect people who voted Labour in 2010/2015 – but were recently wavering – to be saying more positive things about Labour and Corbyn than they had been over the last month. But I haven’t seen any sign of this, for example in the Edelman HuffPost focus groups and Lord Ashcroft’s groups.

All of this feels like an application of one of the lessons from 2015: don’t just read the horserace numbers from the polls. Pay attention to the other numbers and other evidence.

But there was another lesson from 2015 (and the EU referendum) – don’t go with groupthink. So, while many poll analysts are sceptical about the size of the surge and think the true gap must be wider than the latest polls suggest, perhaps the lead really is now just single digits.

It feels unlikely to me that public opinion would shift so much on the basis of two manifesto launches – it sounds like it’s relying on a much closer interest in politics among the public than is normally the case. That said, Stephen Bush – who’s usually right – thinks that opinion really has shifted this much as a result of the campaign.

But perhaps public opinion hasn’t really changed so much and yet the polls are right. Maybe the gap between the parties was always much closer than it seemed. An analogy is with opinion of Bill Clinton immediately after the Lewinsky scandal broke. Unexpectedly, Clinton’s approval rating increased – a change explained by this paper by John Zaller as the result of the public paying more attention to politics when the scandal broke, and remembering that they actually like Clinton:

“there is some “natural” level of support for candidates that is determined by political fundamentals such as the strength of the economy, the candidates’ position on issues and other matters… In non-election periods, the public tunes out from politics… But, when, as in the early days of the Lewinsky matter, Clinton’s capacity to remain in office came into question, the public took stock and reached a conclusion that led to higher levels of support for the threatened leader.”

It’s possible to imagine the same thing happening now in UK politics. For nearly two years most people haven’t been paying attention and polls have been picking up ill-considered responses. But now, many people are thinking seriously about who they would vote for, and, with Ukip largely off the scene and the Lib Dems floundering, many are remembering that they like Labour. This would mean the current polls really could be right.

For what it’s worth I don’t really buy this. It’s not clear to me why this would happen now when it hasn’t in previous elections (the change in the polls now is unusually large). While it’s possible that the shortness of the parliament, the relative newness of both party leaders and Theresa May’s poor performance in the campaign might mean that opinion is particularly volatile, I still find it more plausible that the polls are quite far off and the true gap is currently in the region of 12-14pts. But I’m far from certain.

We will have a better idea from watching polls over the next week – when enthusiasm from the Labour manifesto launch, leading to more poll-taking, could wear off (Ian Warren has some pointers about what to look for) – and focus group transcripts, perhaps showing a change in mood.

I discussed all this on this week’s Polling Matters with Keiran and Matt Singh. It’s one of our most interesting episodes to date and I think well worth a listen.