Tonight sees the publication of the latest full-scale Scottish YouGov poll, and there are some suggestions that it might be the last Scottish poll from any firm before polling day. I must say I find that hard to believe - surely given the unprecedented situation, at least one newspaper is going to fancy the idea of a poll on Wednesday, or even on Thursday morning? Oh well, if this is the last one, the SNP can hardly have any complaints about the state of play it depicts, which is essentially unchanged since the 'second surge' that occurred a few weeks ago.I haven't been able to track down the fieldwork dates yet, although I do know that the poll got underway before theleaders' special on Thursday night, and the revelation that Miliband would be willing in some circumstances to help Cameron stay in power. If it turns out that the bulk of the fieldwork was done before then, we may not be much further forward, because that's the only recent event which seemed to have a reasonable chance of shifting opinion in either direction.If I was going to sound any note of mild concern about the result, it would be over the Liberal Democrat share, which is significantly higher than in any other YouGov poll since the referendum - the previous range has been 3-5%. There are basically three possible explanations for the jump - a) it's an illusion caused by the margin of error, b) it's a real but small increase in Lib Dem support across Scotland, or c) it's a real increase in support driven mainly by tactical voting, and is therefore heavily concentrated in Lib Dem-held seats. The first two possibilities wouldn't present a problem for the SNP, but the third certainly would.There seems to be some confusion over the exact numbers - Anthony Wells at UK Polling Report (who's in a position to know, because he works for YouGov) says it's SNP 49%, Labour 25%, Conservatives 17%, Liberal Democrats 5%. Those figures are absolutely identical to the last YouGov poll, so I'm wondering if Anthony has got the two polls mixed up.And now we have a third slightly different set of figures. The, who commissioned the poll, say it's. Presumably these are most likely to be the accurate numbers, so I've updated the start of the post (the Conservatives were previously on 17%).