This is always a scary time of year for followers of the polls. There are rarely any polls published over the Christmas/New Year period, and there's no reason to automatically assume that nothing will have changed by the time that drought is broken. The very fact that people switch off completely from the news for a few days can sometimes, ironically, shift their voting intentions quite markedly. The parties that have the most to worry about that phenomenon this year are the SNP, who built up such an enormous lead in Scotland over the closing months of 2014, and Labour at GB-wide level, who pulled a few points clear of the Tories in most of the polls conducted just before Christmas.
The first GB-wide poll of the New Year has just been published by Opinium...
Britain-wide voting intentions (Opinium, 30th December - 2nd January) :
Labour 33% (-3)
Conservatives 32% (+3)
UKIP 17% (+1)
Liberal Democrats 8% (+2)
SNP 4% (-1)
Greens 4% (-1)
Plaid Cymru 1% (+1)
BNP 1% (n/c)
So it seems, on the face of it, that Labour's worst fears have been confirmed - their 7-point pre-Christmas lead has essentially evaporated, although only time will tell whether that is a real shift of opinion or simply an extreme example of margin of error "noise".
With the SNP it's even harder to say anything definite, because (irritatingly) Opinium are the only firm that don't publish the results of their Scottish subsamples. The slippage from 5% to 4% certainly isn't anything to worry about, because the figure has consistently been either 4% or 5% in every Opinium poll since the referendum. However, the unrounded figure in this poll is 3.62%, which is a touch lower than in other post-referendum Opinium polls - albeit we're obviously talking about tiny fractions here, given that this is a GB-wide poll.
If you assume that all respondents who said they would vote SNP are resident in Scotland, and if you assume that Scotland's share of the Opinium sample was equivalent to our actual share of the GB population, that would suggest the SNP are on 41.3% of the vote in Scotland, which would almost certainly mean a commanding lead over Labour. Unfortunately it doesn't necessarily work like that, because Opinium (unlike YouGov) filter their results by likelihood to vote, so it's possible that Scotland makes up more than a proportionate share of the filtered sample. It's also likely that at least one or two people who said they would vote SNP don't actually live in Scotland.
The most logical conclusion to draw is that the SNP are probably ahead in the Scottish subsample, but maybe not by quite as wide a margin as in other post-referendum Opinium subsamples. But the margin of error for any individual subsample is huge, so we'll have to await the findings of other pollsters to discover whether this is just a statistical blip.