David Cameron is probably right to play down an Olympics polls bounce, but the reason why is not as obvious as he makes out.

The Financial Times reports that the PM told colleagues:

People are too sensible to confuse a sporting event with their day-to-day lives.

Which is just not true. New rule of politics: never assume people are sensible.

A 2010 paper by political scientists Andrew J. Healy, Neil Malhotra, and Cecilia Hyunjung Mo (via WonkBlog), titled Irrelevant events affect voters’ evaluations of government performance, shows just that:

Does information irrelevant to government performance affect voting behavior? If so, how does this help us understand the mechanisms underlying voters’ retrospective assessments of candidates’ performance in office? To precisely test for the effects of irrelevant information, we explore the electoral impact of local college football games just before an election, irrelevant events that government has nothing to do with and for which no government response would be expected.

We find that a win in the 10 d[ays] before Election Day causes the incumbent to receive an additional 1.61 percentage points of the vote in Senate, gubernatorial, and presidential elections, with the effect being larger for teams with stronger fan support.

The authors also find that the more surprising a win, the stronger the incumbency affect; that the effect seems to occur because the happier people feel, the more likely they are to vote for the incumbent; and that if they are made conscious of their reasoning, the effect of irrelevant events diminishes.

So the real question for Cameron isn't whether people are "too sensible" to confuse a sporting event with their day-to-day lives; it's whether the sporting event makes them happier, and, if it does, who they attribute (subconsciously) that happiness too.

The former question is something we'll have to wait until the end of the games to properly answer. The Opening Ceremony, certainly, resulted in a tremendous outpouring of goodwill nationwide, and while it is still a bit too early to tell (literally – the morning rush hour has not yet begun as I write this), it seems unlikely that the much-feared transport chaos will hurt too many people. Partially, admittedly, because many, fearing the worst, have already gone on holiday/arranged to work from home/told their bosses they are planning to contract smallpox for a couple of weeks, so don't expect them in, OK? But also because most of the nation does not actually live in London, and is experiencing most of the games as a televisual event with no real downsides.

National pride will also play a part in any Olympics boost. If Britain wins a lot of medals, then expect at least some people to wander around feeling a lot cheerier than they might otherwise.

The latter question, though, is harder to answer. If the Olympics does make people happier, is it going to be on such a subconscious level that they just attribute it to whoever's in charge? But unlike most sporting events, there is actually some political relevance to consider. It was, after all, Labour who chose to bring the games to London, and who ensure the bid was a success. But it was the Conservatives who oversaw the high-stakes final stretch. And does more of the credit go to the successive Mayors of London, or to the Governments who were ultimately in charge?

Ultimately, the goodwill effects of the Olympics are likely to be too small, too diffuse, and too unclear in provenance to give Cameron much of a boost in the polls. But the reason for that is emphatically not because people are too sensible. Cameron's just lucky he's not being blamed for a tornado.