Why Polls don't predict Results

The media, their pundits and the pollsters seem to have egg on their face this morning 9particularly newspapers that have seriously outdated headlines) as we wake to discover that it is a narrow victory for Hilary Clinton in New Hampshire and not the predicted Obama landslide. It seems the polls got it wrong again! Well perhaps it is really the fault of those who use the polls. Polls are good fun, and often without them there would be no news stories during elections, but even if they ask the right question of the right people they cannot tell us who will win the party nominations in the US and it is doubtful if they can truly predict who will win the presidency unless it is a non-contest; this is why.

1. Polls are context specific

While rolling polls can iron our problems and identify changes in opinion, any poll is related entirely to the moment when the question was asked. The Obama surge may have been linked to his appearance as a winner on the media, so before the New Hampshire campaign got more intense, or there may have been a post-Iowa sympathy surge to Hilary Clinton; either way the results can be outdated and changed very quickly.

2. Polls effect turnout

Polls can be an indication of support but they are not predictive of actual behaviour. The disparity between poll and result may be a reflection of individuals who support Obama, would go to a caucus if their vote mattered, but assumed it did not; so they stay indoors in the warm and actual support seems lower. Alternatively the polls may have mobilised the Clinton supporters in the fear that she would lose. Either way anything but a marginal result can either mobilise or depress turnout; why do you think that TV presenters when running a phone poll tell viewers the results could not be closer, they haven't a clue but it encourages voting!

3. Polls effect results

But polls may also make people question their support. Supporting Obama, the great rhetorician and orator, may be different than wanting him to be President. Voters may have considered whether another Democrat (Clinton) had a better chance of winning the White House, or they don't actually want him as President, or they do want Hilary; whatever the various reasons people may have changed their minds between poll and vote.

4. The mystical caucus

While voting can always prove unpredictable, a caucus is something different. Here it is about face to face persuasion by campaigners for each of the candidates. It is here that prejudices can be played upon, beliefs eroded, hard arguments can have impact; all the tricks come into play here. Maybe evidence of Hilary's record and experience made some Obama supporters question their allegiance; or maybe Edwards' supporters were more swayed by the Clinton team. Whatever it makes for a very unpredictable outcome.

So for those four reasons, all of which may well be happening at the same time to skew results one way or the other, polls should be taken with a pinch of salt and a degree of intelligent scepticism until the results actually emerge. If not you get headlines wrong, assume too much and look very daft when the results emerge.