Canvassers are least likely to meet Nick Clegg's young voters (and they're also the least likely to vote)
Ben Brogan, blogging for The Telegraph, wrote yesterday that "the pollsters are all wrong" - on the doorstep, he says, there's no evidence of a LibDem surge.
I spoke yesterday to a Conservative MP, who had been cavassing in a LibDem/Conservative marginal, and whose veracity I also trust, who said the same thing: he'd met almost no-one who said they had switched their vote to Nick Clegg.
And yet all five pollsters, two online and three telephone, have measured the surge, all within the margin-of-error of each other. My own view: pollsters and canvassers can both be right.
Our own figures show the surge as disproportionately among the young, the 18 to 30 year olds. And this is the demographic you're least likely to encounter on the doorstep.
It's also the age group least likely to vote. Will the surge go all the way to the ballot box?
No idea. I've no way of knowing. This could be a form of the froth I've alluded to before. Clegg's mission will be to invigorate the hard-to-get-out-vote. Cameron might have the advantage of a more reliable segment of the population.
Stephan Shakespeare is CEO of YouGov.