It’s starting to look as if Sol Lebovic, former head of Newspoll, has too much time on his hands since his retirement. The Australian has a habit of wheeling him out to give respectability to otherwise bizarre poll interpretations. Now The 7.30 Report is using him as well, last night in a double act with Antony Green.

Lebovic’s particular obsession this year has been the notion that large numbers of voters don’t make up their minds until the last minute. Back in July, Quadrant had him telling Frank Devine that “half the voters make up their minds during the campaign and a third not until the last week”. (At the time, I suggested that he was pulling Devine’s leg.)

Last night he was a bit more circumspect, saying “we do know in previous elections about one in four voters said that they finally decided who to vote for in the final week of the campaign.”

That’s still utterly unbelievable. If decision-making was happening so late in the piece, we would expect much bigger variations in the polls, and much more diverse swings on election day. The evidence is that, on the contrary, Australian electoral behavior is very stable and predictable.

One of the first rules about polling is to ask yourself whether respondents have any systematic reason to lie. In this case, the answer is yes: when questioned about when they “finally decided” how to vote, people like to sound open-minded and thoughtful, so they don’t admit to having made up their minds well in advance. (For the same reason, 20% claim to vote below the line for the Senate, even though the real figure is less than half that.)

If you put the question differently, you can get quite different responses: polls that ask for voting intention get much lower numbers of “undecided”, because people don’t like to appear indecisive.

And the problem is metaphysical as much as epistemological: just what is it that these questions are (badly) measuring? What does it mean to make up your mind at a certain date? Is it that you were in some way undecided beforehand, or still actively considering options, or just that there was some theoretical possibility you might have decided differently?

But the media like Lebovic’s line, because it makes contests seem more open and exciting than they really are. With another three weeks to try to hold people’s interest, that’s a big consideration.