Leave open up 4-point lead in dramatic YouGov poll

The psychology of the EU referendum race has certainly shifted rapidly.  It seems like no time at all since we were looking at opinion poll evidence of a potentially decisive swing to Remain, and weighing it up against other poll evidence suggesting that nothing much had changed.  Now the only realistic question is the opposite one - has there been a sizeable swing to Leave?  The biggest reason for thinking there may well have been is the most recent ICM telephone poll, which showed a completely unprecedented outright lead for Leave.  But there hasn't been any other phone poll since then to corroborate or undermine that finding, and the ORB phone poll that was conducted at more or less the same time was murderously difficult to interpret (mainly because the trend in the ORB phone series has been as mad as a bucket of frogs from the word go).

We've had a few recent online polls, which weren't particularly conclusive either.  ICM's own online poll and last night's Opinium poll both reported a swing to Leave, but not on the same scale as the phone poll, and in neither case were the headline figures outside the 'normal range'.  Last week's YouGov poll showed no movement in either direction, although that wasn't necessarily inconsistent with a swing to Leave, especially given that the previous poll from the same firm had shown a pro-Leave shift.  The standard margin of error can conceal a swing that is actually happening just as easily as it can generate a false impression of movement when everything is static.  Tonight's new YouGov poll would tend to support that interpretation, because it comes into line with ICM and Opinium by showing a 4-point boost for Leave.

Should the United Kingdom remain a member of the European Union or leave the European Union?

Remain 41% (n/c)
Leave 45% (+4)

So just how good is that for Leave?  It's quite hard to say whether a 4% lead is within the 'normal range' for YouGov, because they certainly haven't reported a Leave advantage as big as that for several months, and yet if you travelled back in time to the winter or autumn, tonight's result would seem reasonably routine.  Strangely, the sudden boost for Remain that occurred towards the end of February appeared to be a YouGov 'house effect' - other firms weren't picking it up, so it's impossible to know for sure whether the fact that it's now being reversed is directly linked to the Leave surge that's been reported by other firms.  But it's hard to escape the impression that a pattern is emerging.

The case for the defence as far as Remain is concerned is that tonight's TNS poll doesn't show any movement to Leave (although it does show a modest Leave lead).  However, the fieldwork is ancient, so in reality it doesn't contradict other firms' findings at all.

I had a sort of epiphany tonight when I saw Doug Daniel's reaction to the YouGov poll.  This is what he said on Twitter -

"I remember back during the proper referendum when we would've thought this meant we were winning. 14% undecided."

"folk will s**** it just like they did in 2014."

It suddenly struck me that the outcome of this referendum is going to affect the chances of a second indyref in more ways than one.  As of this moment, there's a very strong assumption that there's always bound to be a substantial late swing against the change option in any constitutional referendum.  So if that myth is proved to be false over the coming weeks (I firmly believe it is false, but if it's very visibly proved to be false), it's going to affect people's thinking quite profoundly.  It's certainly going to be pretty hard to sustain the ultra-cautious line that we need an implausibly huge opinion poll lead for independence over a sustained period of time before we can even think of going to the people again.  On the other hand, if the Leave vote does collapse as polling day approaches, the Caution Faction will feel further emboldened (if that isn't a contradiction in terms).

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SCOT GOES POP POLL OF POLLS

We've reached a stage in the campaign where a three-week time-frame for the Poll of Polls seems far too long - polls are coming thick and fast, and public opinion may be changing very quickly.  To keep the sample as up-to-date as possible, from now on I'm only going to include polls that were at least partly conducted within the last two weeks.

50/50 ONLINE/TELEPHONE AVERAGE :

Remain 43.9% (-1.7)
Leave 43.2% (+1.6)

ONLINE AVERAGE :

Remain 42.1% (-0.2)
Leave 43.3% (+0.4)

TELEPHONE AVERAGE :

Remain 45.7% (-3.2)
Leave 43.0% (+2.7)

(The Poll of Polls takes account of all polls that were conducted at least partly within the last two weeks. The online average is based on seven polls - three from YouGov, one from TNS, one from Opinium, one from BMG and one from ICM.  The telephone average is based on three polls - one from ORB, one from ICM and one from Survation.)