There are two new polls out this morning. Only one, however,from Survation for the Daily Mail, was conducted after last week’s co-ordinated announcement that Scotland would not be allowed to share the pound with the rest of the UK, an announcement that the No side hoped would bring them a significant boost. The other, from TNS BMRB, is as much as a fortnight old, though that does not mean it is not of any interest.

At first glance the Survation poll represents remarkably good news for the Yes side. As compared with the company’s previous poll, conducted just a fortnight ago, support for the Yes side is up six points from 32% to 38%, while the No tally is down five points from 52% to 47%. Once the Don’t Knows are excluded the Yes vote is up from 38% to 45%.

However, at this point a large caveat is in order. As regular readers of this blog will remember in their previous poll Survation weighted their sample by how people said they voted in the 2010 UK general election. That decision almost undoubtedly served to depress the estimated Yes vote and flew against evidence from ICM and Panelbase that people were better able to remember how they voted in 2011 than in 2010. This time Survation have weighted their sample by people’s reported 2011 vote, a decision that in this instance means that their weighting has very little impact on their estimate of the Yes and No vote.

Still, Survation’s 45% Yes vote is hardly the figure that the No side will have expected any poll, however conducted, to have turned up following last week’s currency announcement. It is certainly higher than the average of 41.5% recorded by the last six polls (excluding Survation’s own) conducted before the announcement. It is also rather higher than the 43% figure in Survation’s own previous poll prior to it being weighted by 2010 vote. Meanwhile although 22% say they are now more likely to vote No as a result of the UK announcement, slightly more, 29%, say they are less likely to do so.

In short, however one looks at this poll, one has, at minimum, to conclude that it offers no evidence that the currency intervention has delivered the No side any immediate boost.

The poll gives us some clues why that might be the case. Only 48% of voters say they would like Scotland to share the pound in the first place. Just 37% are convinced that Westminster is not bluffing when it says it will refuse to share the pound – though perhaps the 26% who say they do not know could yet be convinced. Meanwhile 52% think that a monetary union would be in the interests of the rest of the UK (which might be one reason why they do not take Westminster’s threat seriously).

In truth, however, the poll shows not a nation reacting in unison to the currency developments, but rather one reacting in opposite directions. Yes voters think that Westminster is bluffing (73%), that it is in the rest of the UK’s interests to allow Scotland to share the pound (86%), and also that it is OK for Alex Salmond to threaten not to take on Scotland’s share of the UK debt should currency union not happen (62%). No voters in contrast feel Westminster is not bluffing (65%), are inclined to the view that it is not the interests of the rest of the UK to share the pound (47%) and that Scotland should not threaten to refuse to take its share of the debt (64%).

In short, it looks as though those who were already convinced Yes voters have been willing to follow Mr Salmond’s line, while those who were already confirmed No voters have applauded the UK government view – albeit somewhat less enthusiastically. To get some idea of whether either side actually convinced voters in the middle we are best looking at the responses of the 16% of Survation respondents who say they are undecided.

The figures do not make comfortable reading for the No side. Undecided voters are rather more likely to think that Westminster is bluffing (27%) than that it is not (18%) and are as least as likely to think it is OK to suggest that Scotland might not accept its share of UK debt (29%) than believe it is not (27%). Above all, while 18% of undecided voters say they are now more likely eventually to vote No, as many as 23% indicate that they are more likely to vote Yes. Those are not figures that suggest that voters in the middle have been persuaded to back the Union in order to keep the pound, as No strategists suggested they would be.

Still, the poll does raise some questions for the Yes side. In particular, even a majority of Yes voters (59%), let alone of all voters (65%), think that Mr Salmond should spell out his currency Plan B in case a currency union does prove impossible to forge. Moreover, Yes voters are far from agreed on what that alternative should be. While 29% would like Scotland to have its own currency that is pegged to the pound, 23% would like to use the pound unilaterally, and 20% would prefer a fully floating separate currency. Corralling them all around an agreed alternative may not prove easy.

At first glance, the TNS BMRB poll looks very unexciting. Its estimate of referendum voting intention – 29% Yes and 42% No – is exactly the same as in its previous poll, conducted earlier in January for Sir Tom Hunter. However, with an estimated 41% Yes vote once the Don’t Knows are excluded, that previous poll was the highest Yes vote yet recorded by TNS BMRB. Now that that figure has been replicated, we have further evidence that the No lead did indeed narrow somewhat in the weeks immediately before the currency announcement. A little more unwelcome news for the No side to contemplate.