The SNP have released a new poll they commissioned from Survation, which undermines Labour's pitch by suggesting that more people (37.4%) think that a vote for the SNP is best able to prevent a Tory government than think the same about a vote for Labour (35.2%). There are no voting intention figures published, but it's possible to get more than a rough idea from the raw numbers provided at the top of the datasets. This is how it seems to work out -
Liberal Democrats 4.1%
If the voting intention figures ever see the light of day (and they may do, because the monthly Survation poll for the Record must be due soon, and the SNP's question may have been a bolt-on to that), they won't be exactly as above, because the turnout filter would be applied. But it certainly looks as if the SNP's lead hasn't slipped at all from the 17% reported last month, and may even have increased slightly.
This doesn't really take us forward all that much, though, because the poll's fieldwork is slightly out of date, and took place at the same time as the recent YouGov poll, which similarly showed a more or less static position. Perhaps more interesting is the Scottish subsample in this morning's GB-wide YouGov poll, which shows an entirely typical lead for the SNP of 44% to 26% - in spite of the fact that Labour's Britain-wide vote of 36% is the highest recorded so far this year. Wherever those extra votes for Miliband are coming from, they're not coming from Scotland.
On the SNP's own question, the most interesting detail is that 25.4% of people who voted Labour in 2010, and even 18.3% of the rump Labour vote from 2011, think that the SNP are best placed to get the Tories out. Those people alone would be sufficient for the SNP to make big inroads. Liberal Democrat voters from both 2010 and 2011 split in favour of the SNP being the best anti-Tory option, although in their case it may not be entirely clear whether they think that's a good thing or a bad thing.