Heartbreak for Ruth as SNP enjoy double-digit lead in a poll conducted prior to the Tory manifesto meltdown

With all due respect to the Herald, I fail to understand what earth-shattering insights we're supposed to glean six days before a general election from the publication of a poll that was conducted between two and three weeks ago.  Yes, the "new" BMG poll is part of a regular series and the long delay between fieldwork and publication is not untypical, but during the heat of a campaign everything becomes very compressed, and (as we've discovered) it's possible to get significant shifts of opinion over the course of a few days that might otherwise take weeks, months or years.  If it wasn't feasible for BMG to get their numbers out a bit quicker this time, I struggle to see the point of the exercise.  It even looks like almost all of the fieldwork preceded the disastrous Tory manifesto launch, which means the poll practically comes from a different political era.  However, for what it's worth, here is BMG's estimate of what the state of Scottish public opinion was quite a long time ago...

Scottish voting intentions for the UK general election (BMG, 12th-18th May) :

SNP 43%
Conservatives 30%
Labour 18%
Liberal Democrats 5%

There's nothing remotely surprising about those figures - they're pretty much bang in line with what other firms were showing during the earlier part of the campaign.  We know with a high level of confidence that there has been a Labour recovery since then, and that the Tories' second place is now under some kind of threat.  But what is much less clear is whether the extra Labour votes have come predominantly from the Tories themselves, from the SNP, or from both parties roughly equally.  Until that question has been answered, it's a bit redundant of the Herald to be using ancient polling data in an attempt to fuel speculation that Angus Robertson is under threat of losing his seat in Moray.  If there has been direct movement from Tory to Labour since the BMG poll was conducted, that threat may have receded somewhat.  The much bigger 18% SNP lead in the more up-to-date Ipsos-Mori poll would tend to support that interpretation, but isn't sufficient as proof.  What we really need are updated figures from a firm that has already polled during the campaign.