Ipsos-Mori consolidate their status as the extreme outliers

One thing that we can certainly deduce from yesterday's Ipsos-Mori poll is that the Yes campaign are highly unlikely to go into polling day in September in the lead with that particular pollster. But the million dollar question is whether they actually need to do so. The gap between the No lead being shown by Ipsos-Mori and the average No lead being shown by the four online pollsters that have reported so far this year is a stonking 12.25%. In other words, even if the online pollsters end up pointing to a narrow Yes victory by September, the chances are that Ipsos-Mori will still be showing a double-digit No lead. They really have turned into the extreme outliers of this campaign.

That's not to say they are necessarily getting it wrong, of course. They are unique in being the only referendum pollster to be carrying out their fieldwork by telephone, and because of that factor it's hard to shake off the nagging doubt that they may be getting a more representative sample than the online pollsters (at the very least, there's no danger that they're interviewing the same people over and over again as YouGov and Panelbase do). Luckily, however, we do have one other non-online pollster to make a comparison with. TNS-BMRB conduct their fieldwork face-to-face, and in recent polls have been showing a markedly more favourable position for Yes than Ipsos-Mori. So the non-online status of Ipsos-Mori can't in itself explain why they produce such different results from everyone else. A more likely explanation is their ongoing refusal to weight their results by past Holyrood vote, which is now standard practice for most other BPC pollsters. It's also known that they use a 'stealth preamble' when asking the referendum question, but we can only guess how leading or biased that may be.

And whatever the virtues of telephone polling (or indeed face-to-face polling), we shouldn't forget that there's one very good reason for thinking that online polls may be producing more accurate results, namely that 'shy Yes' voters probably find it harder to admit their preference to a live interviewer than to a computer screen.

All the same, this huge degree of uncertainty as to the true state of play is incredibly frustrating and unsettling. If ICM (the UK's "gold standard" pollster) and their online polling cousins of Panelbase and Survation are correct, the Yes campaign are within relatively easy striking distance of victory and an independent Scotland in 2016 is a real prospect. But if Ipsos-Mori are correct, the challenge faced by Yes is bordering on the insurmountable. I know most of us firmly believe that the former scenario is far more likely, but it's scary to think that we simply won't know for sure until the real votes start coming in.

As ever, when pollsters are so far apart the only way of making sense of any individual poll is to look at the trend, and Ipsos-Mori have at least confirmed that the No lead remains three points lower than in the last two polls prior to the publication of the White Paper.

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SCOT GOES POP POLL OF POLLS

Since the No vote is unchanged in the Ipsos-Mori poll, it's only the Yes vote that is affected slightly in the updated headline figures of this blog's Poll of Polls.

MEAN AVERAGE (not excluding Don't Knows) :

Yes 34.6% (-0.3)
No 48.9% (n/c)

MEAN AVERAGE (excluding Don't Knows) :

Yes 41.4% (-0.2)
No 58.6% (+0.2)

MEDIAN AVERAGE (excluding Don't Knows) :

Yes 42.0% (n/c)
No 58.0% (n/c)

(The Poll of Polls is based on a rolling average of the most recent poll from each of the pollsters that have been active in the referendum campaign, and that adhere to British Polling Council rules. At present, there are seven - Angus Reid, YouGov, TNS-BMRB, Survation, Panelbase, Ipsos-Mori and ICM. Whenever a new poll is published, it replaces the last poll from the same company in the sample. Changes in the Poll of Polls are generally glacial in nature due to the fact that only a small portion of the sample is updated each time.

For clarity, the Poll of Polls takes no account of polls conducted by bridalwear companies.)

The fact that the median average has become more favourable to Yes than the mean average is testament to how the Yes-friendly end of the polling spectrum is now more heavily populated than the No-friendly end, a complete reversal of the position that held good until recently.