science!
Here’s something interesting. I grabbed the last 6 months’ worth of national opinion polls from Wellsy’s and graphed the Tory lead in percentage points. On the tiny chart below, you’ll observe that the mean is 10 points; the hatched area shows one standard deviation each side of the mean, and I’ve plotted a linear trend through it. (You can see a full-size version of it here.)
The interesting bit; there are 21 polls, out of 158, that showed a Conservative lead of more than one standard deviation greater than the mean. All of them occurred before the 29th of January. There are 24 that showed a lead more than one standard deviation less than the mean. 20 out of 24 occurred since the 19th of February. What on earth could have happened between these dates?
The posters broke in a big way around the 19th of January and the second wave hit in early February. Clifford Singer deserves a knighthood for this.
(link)
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World of Harrowell
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Alternate Seat of TYR 
March 28, 2010 at 3:04 pm
Yes, but was that real derision or manufactured derision? Serious point: if people already thought Dave was that ridiculous, how come the Tory lead was so solid beforehand? And if they didn’t, how come it melted away so quickly? These are deep waters, Gromit.
March 28, 2010 at 5:33 pm
Regarding real vs manufactured derision – compare the Cash Gordon fuckup and MyDavidCameron….
Was it solid? There was a lot of anecdotal reporting that suggested the support was thin, and a lot of people were surprised that the Tories couldn’t break 40%. Of course, anecdotal evidence is another word for qualitative interviewing. It’s quite possible that there were a lot of people leaning superficially to the Tories.
March 28, 2010 at 4:06 pm
George Osbourne. Lord Ashcroft. Labour getting their act together.
March 29, 2010 at 4:09 pm
You know the polls will still underestimate the Tory share though, weighting or no.