As well as the GB voting intention figures in the Telegraph, the SNP also released figures for voting intention in Scotland from their latest YouGov poll. Topline figures, with changes from YouGov’s last Scottish poll in mid-March are

Scottish Parliament constituency voting intention: CON 15%(+1), LAB 30%(-4), LDEM 13%(+1), SNP 37%(+2)
Scottish Parliament regional voting intention: CON 15%(nc), LAB 28%(-4), LDEM 13%(+2), SNP 37%(+7)

Westminster voting intention: CON 21%(+1), LAB 32%(-5), LDEM 13%(+2), SNP 30%(+3)

In every case we have Labour dropping, with the SNP the largest beneficiary, albeit the other parties also gain. Asked who would make the best First Minister Alec Salmond is dominant, picked by 36%. He is followed, perhaps surprisingly given the Conservatives comparatively poor position in Scotland, by Annabelle Goldie on 10%, with Ian Gray on 7% and Tavish Scott on 4%.

The Times is reporting a snap Populus poll, which interviewed 500 or so people on Wednesday night. The sample obviously isn’t large enough for accurate voting intention figures, but gives us the first – rather mixed – signals of how the budget wasa received.

Most of the measures in the budget were supported. 65% supported the increase in the ISA limit, 58% supported the stamp duty holiday, 47% the scrappage scheme. 57% supported the new higher rate of 50% tax, with 22% opposed. The only specific measure to run into strong opposition was the increase in fuel duty, opposed by 68%.

Budgets, however, are more than the sum of their parts. Just because the tax changes in them are popular, doesn’t mean the overall package is, or that they don’t have a wider effect on how the government is perceived. So, while the 50% tax band was very popular, people were split on whether it was fair, and 53% agreed it was “the end of New Labour”.

A positive sign for Labour was that Brown & Darling once again lead Cameron & Osborne on the economy. Rather more omnious for them though is that 58% agreed with David Cameron’s attack on the government that “all Labour Governments end up ruining Britain’s public finances by spending too much”.

Something of a mixed bag there then, hopefully we will see the effect on actual voting intentions later tonight.

The tables for MORI’s monthly poll are now up on their website so we can dig around inside them and look at the maths. Obviously with such a surprising shift in support, the thing I looked at first was Liberal Democrat support. What actually caused that jump in their figure?

The sample itself wasn’t massive more Liberal Democrat – last month 9% of the sample said they had voted Lib Dem in 2005, this month 10% said they had. The raw numbers of people saying they were voting Lib Dem were up from 17% to 20%, but again, that’s a lot less than 8 points! A major factor seems to be the filtering by likelihood to vote.

I have written a long article on the site here looking in detail at how pollsters deal with likelihood to vote. The simplified version though is as follows…

YouGov ignore it,
Populus – weight by it, so someone who says they are 9/10 likely to vote is worth 90% of someone who says they are 10/10 likely to vote (and so on),
ComRes – do similar, but entirely exclude those who are less than 5/10 likely,
Ipsos MORI – filter by it, so someone who says they are 10/10 likely to vote is counted, and someone who says they are 9/10 likely to vote (or lower) is excluded,
ICM – also filter by it, but less strictly, taking those who rate their chances at 7/10 or higher.

In last month’s MORI poll, of all the people who said they would vote Liberal Democrat, only 47% of people said they were 10/10 certain to vote. In this month’s MORI poll 69% of Liberal Democrats said they were 10/10 certain to vote, so a much larger proportion were included in the topline voting intention, contributing to the massive increase in Lib Dem support.

Interestingly though it wasn’t a massive shift in the likelihood of Lib Dem supporters to vote. Last month 81% of Lib Dem supporters said they were 7/10 likely to vote or above. This month 85% of Lib Dem supporters said they were 7/10 likely to vote or above. What actually happened is that lots of Lib Dem supporters who had said they were very likely to vote, rating their chances at 7 to 9 out of 10, moved to saying they were certain to vote, but because it tipped them over the 10/10 point it moved them from being excluded from the poll to being included. It’s the result of having a straight cut off, rather than a scale like ComRes & Populus do.