What election polls do not tell us

"...in spite of the useful information that election polls offer, they are lacking in two important respects..."

We can expect a large number of election polls to be published in the next four weeks. Not all polling agencies arrive at their numbers in exactly the same way, and they need to be read with care. And in spite of the useful information that election polls offer, they are lacking in two important respects, both of which relate to the difference between ‘hard’ choices and ‘soft’ ones.