Here's a question for you. Obviously it's too much to ask that national newspapers provide a critical view of polling methodology. And there are obvious problems in criticising a poll your own paper paid for on the front page. So bloggers will probably just have to do it. But here goes. To what extent is the quality of "being prime ministerial" caused by being prime minister?
The polls haven't been great for Labour over the turkey gap, and we know this is probably a thing because it wasn't just one poll or one pollster's polls that showed it. Fair enough. The problem is, of course, that given this information, everyone immediately starts trying to impose stories on it. Some of this is pure wind, but at least some of it tries to be based on data.
The Guardian is very exercised by one of the down-ticket questions in their own ICM poll, which apparently shows that more people think David Cameron is "good in a crisis" than Ed Miliband. The problem with basing any conclusions on this is that it's quite possible that being Prime Minister gives you lots of crises to be good in, and plenty of resources to help you be good in them, like the advice of expert civil servants and the wiles of some of the world's most accomplished bullshitters. Further, as crises in our political system naturally migrate towards No.10 Downing Street, there is a permanent media stage on which you can perform prime ministership.
Obviously, crisis management is a desirable skill in a prime minister, but the job of Leader of the Opposition is not one that gives you lots of opportunities to display it. In fact, as the opposition isn't in charge, it has no excuse for getting into crises in the first place. A Leader of the Opposition who is having crises can only be having them because their party is being disloyal, because a shadow cabinet member is in trouble, or because they are themselves in trouble personally. The Prime Minister gets crises delivered every morning by the civil service in a red box, like an unappetising catered breakfast. It is hard to think of a situation where an opposition leader can demonstrate the ability to deal with crises that is not, per se, very bad news for the opposition.
In fact, the only one I can think of is the situation where a member of the shadow cabinet is being disloyal and has to be sacked to put a stop to the fitna, as it were. And, well, that already happened. To be honest, how many people actually care, though?
So what I would like to see is the following analysis - let's pull some of those so-called soft questions ("good in a crisis" would be a start) and compare the ratings for various politicians before and after becoming Prime Minister (and for extra credit, before and after joining the Cabinet). (Anthony Wells, dear heart, do you happen to possess such a data series?) My hypothesis is that there will be a statistically significant uplift for all of them, and that therefore much of this comment is content-free.
Wellsy does have a consistent series for the "best Prime Minister" question, here, which shows that Cameron's score rose 10 points from early May to September 2010. Gordon Brown went from 30 to 44 between the end of May 2007 and mid-August. The only other comparison in the series is the 2005 general election, in which Tony Blair went in as prime minister and came out as prime minister. I pulled the data for all three PMs over roughly the same periods of time, covering the changes of PM in 2007 and 2010 and the 2005 election, and excitingly, Blair's rating didn't show any significant change, which is what you'd expect if I was right. The move was 2.8 and 2.5 standard deviations respectively for Cameron and Brown and 0.67 for Blair, and the series is roughly normally distributed, so this result is statistically significant at the 99% confidence level for people becoming PM and insignificant for the no-change case.
You could argue that David Cameron became prime minister because people thought he would be better, but of course this wouldn't be true of Gordon Brown as there was no election in 2007, and we get the same result. I did wonder if there might be a seasonal effect (he's like a pound-shop Chris Dillow!), but Brown's ratings didn't do anything interesting over the summer of 2006 and neither did Blair's in 2005.