Tonight’s YouGov poll for the Sunday Times has topline figures of CON 33%, LAB 42%, LDEM 8%. The nine point Labour lead is very much in line with the ten point leads YouGov have been showing all this week (though given the turbulent week the government have had I suppose the fact that things don’t appear to have got even worse is itself notable!). I will do a full write up of the poll tomorrow.

The only other Sunday poll I’m aware of is ComRes in the Sunday Indy which didn’t have voting intention, just my beloved agree/disagree statement grids. The most interesting one on there is the proportion of people agreeing with the statement that they trust David Cameron and George Osborne with the economy, agreement with with was down 4 to 24%, disagreement up 11 to 60%, a big increase in the proportion of people disagreeing.

Following the ten point lead from ComRes yesterday tonight’s YouGov poll for the Sun has topline figures of CON 33%, LAB 43%, LDEM 9%. This is the first time Labour have managed a double point lead from YouGov since March last year.

With any shift in the position in the polls it’s natural to look for an explanation, and there’s always a tendency to read what you want to see into the change. Far too often I see people in the comments here confidently ascribing any change in the polls to their own pet issue, or to what they’d most like the public to feel strongly about.

Right now we don’t really now what the cause is, though there are some obvious candidates. First we should consider the longer term trends – it’s always tempting to assume whatever has just happened explains movement, but remember there was already a trend towards Labour before the budget, be it the unwinding of the European “veto” effect, an improved performance by Ed Miliband or the increased prominence of the NHS as an issue.

Secondly there is are the issues in the budget, the two most unpopular being the 50p tax rate and the “granny tax”. Thirdly is the cash for access story that sprang up over the weekend. Fourthly there is the combined affect of all them, the culumulative image of a government in trouble you get when lots of bad news stories come all at once (take for example Labour’s “Black Wednesday” in April 2006 when they were hit with the foriegn prison scandal, John Prescott’s affair and Patricia Hewitt being heckled by nurses in a single day).

Right now we don’t really have enough evidence to judge by – you can’t ask people why they’ve changed their vote as most people are very poor at understanding or reporting their motivations. The best measure is proper tracking data on whether more people see the government as sleazy or corrupt, or close to the rich, or distant from pensioners than they did before. Hopefully that will come in time.

Personally my guess (and it’s not much more than a guess at this stage) is that the “granny tax” has done the most damage. Most people already saw the Conservatives as being more interested in the rich than people like themselves, and people have a low opinion on all the parties on issues of sleaze and favours for donors. In many ways these would only have confirmed and entrenched existing negative perceptions (the Pope does not suffer an anti-Catholic backlash when he talks about God, people tend to already see him as Catholic). However, in the past comparatively comfortable pensioners have been a bedrock of Conservative support – a tax hike specifically hitting a natural group of Conservative supporters who probably did see the Conservative party as one which looked out for people like them is liable to do damage… and lo and behold, in YouGov’s polls since the budget we’ve seen significantly lower Conservative leads in the over 60s break than we are used to (today the Conservatives have a six point lead amongst over 60s, better for them than yesterday, but before the budget double-point leads were the norm). That said there is never a single cause – I’m sure the other factors have made their own smaller contributions too.

The weekend after the budget often sees several polls. Tonight I am expecting at least three: the weekly YouGov poll for the Sunday Times, an ICM poll for the Sunday Telegraph and a Survation poll for the Mail on Sunday. I’ll update as they come in…

UPDATE: The ICM poll for the Sunday Telegraph has topline figures, with changes from their poll for the Guardian just before the budget, of CON 37%(-2), LAB 38% (+2), LDEM 13%(-2). It shows a slight shift towards Labour since the budget, though the one point Labour lead is smaller than some others we’ve seen of late for methodological reasons that we’ve discussed here before.

The other questions in the ICM poll showed the same patterns of popular and unpopular measures as in the YouGov/Sun poll after the budget: majorities were in favour of the increase in the personal allowance, to stamp duty and the cut in corportation tax. 63% opposed the abolition of the age-related tax allowance and 56% opposed cutting the top rate of tax to 45p.

UPDATE2: YouGov for the Sunday Times has topline figures of CON 35%, LAB 42%, LDEM 10%. This follows on from an eight point lead in YouGov’s Wed-Thurs poll for the Sun, so adds further weight to the evidence that the budget has produced a shift towards Labour.

UPDATE3: And finally, the Survation poll for the Mail on Sunday has topline figures, with changes from December of CON 31%(-4), LAB 39%(+4), LD 11%(-3), Others 19% (the high others is due to Survation prompting for UKIP in their main voting intenton question, consequently putting them at 8 points).