Did Hackgate damage the Conservatives?

There is a post over on Conservative Home rounding up the polling at the end of year. While some of it is somewhat optimistic for the Tories (for example, I probably wouldn't say that the public back Osborne over Balls as best Chancellor - when YouGov last asked it 25% chose Osborne to 23% for Balls, so close to one another as to make no real difference. I'd characterise is as the public being less than enamoured with either or them!) there's nothing that I'd violently disagree with, though it does rather gloss over public concern about the government's economic policy, which the public tend to back through gritted teeth rather than any enthusiasm (polls consistently show that people think cuts are too deep, too fast and bad for the economy... but are necessary none-the-less. People don't like the medicine, think it may be making things worse, but see no alternative).

The interesting question though is ConHome's first point - did "Hackgate" damage the Conservatives? Taking one single day's poll each month is needlessly simplistic when you've got a poll a day, much better to take the average of each month. Hackgate really broke around about the 4th July, when it was revealed that Milly Dowler's phone had been hacked (obviously the story had been rumbling for years before, but that was the point it boiled over). In June the daily YouGov polls had the Conservatives on an average of 36.8%, in July the average was 35.8%. The average Labour lead in June was 5.5 points, in July it was 7 points. Those differences would not be significant between two individual polls, you'd rightly dismiss them as random margin of error. Between averages of 20-odd polls in each month, they show a genuine movement.

So, is it cut and dried that "Hackgate" did damage the government? Not sure - let me give you two alternative scenarios. The graph below shows a rolling five day average of the YouGov daily poll since last October, with the monthly average lead in each calender month.

We can see the Conservatives still in the lead late last year, then Labour pulling ahead in January as the country went into negative growth and concerns over the economy and the government's economic policy grew. That trend continued and peaked in March, with an average Labour lead of 7.2 points. After that it drops - why? There are a number of possible reasons, there was more positive economic news for a while, perceptions of Ed Miliband were beginning to sour, a fair chunk was almost certainly due to the local elections and the perception that the Conservatives had done better than expected and Labour worse. Either way, in May the average Labour lead was down to 4.1 points. Since then the Labour lead has been on the rise again.

So, one explanation is that the Labour lead has risen because of "hackgate", perceptions of Miliband improved (which on the evidence we have is indisputable, though who knows if it will last), doubts over the government have increased and it has had a small but definite effect on voting intentions.

The alternative explanation is that the Labour lead was rising anyway due to other factors - it rose by 1.4 points between May and June, then 1.5 points between June and July. If that's the case it could be down to fading effect of the local elections and worsening economic tidings, with hackgate just a brief blip on a pre-existing underlying trend. Clearly there is no way of knowing for sure - perhaps the best view to take is that Hackgate may or may not have contributed to the ongoing drift of support away from the Conservatives towards Labour.