When big polling leads mean big election results

Antony had a good post over on his blog today about how the current big polling leads Labor enjoys may not end up flowing through to a large election victory. My own view on the subject is that I’m completely and utterly open minded about the prospect – it’s worth explaining why.

If we look back over the last 10 years or so of federal and State politics, there’s been a number of examples where political parties have enjoyed large and consistent polling leads. In fact, there’s been five really strong examples where a party has completely dominated the polling for most or all of their term, and two moderately strong examples where a party dominated the polling late in their term. Of the 7 times a party has dominated the polling, on 6 of those occasions the party has gone on to get election results consistent with those large polling leads.

The only exception was Kevin Rudd and Labor in the 2007 federal election.

The other interesting thing to note is that when you just look at incumbent governments and their polling, of the six incumbent governments that experienced big polling leads, all six of them went on to win large election victories consistent with those big polling leads.

First up, we’ll take a look at the five strong examples of polling domination in Qld in 2001 and 2004, Victoria in 2002, South Australia in 2006 and the Federal election in 2007. We’ll track the polling on both primary vote terms and estimated two party preferred terms through to the actual election result using Newspoll data. I had to construct a two party preferred estimate for some of this polling (Qld, NSW and Vic) as Newspoll either didn’t measure or didn’t publish that estimate (click the charts to expand).

Next, the two weaker examples of NSW in 1999 and 2003, where large polling leads eventuated, but relatively late in the terms.

If, for these seven cases we have where large polling leads existed, we take the average of the Newspolls for the 12 month period leading up to the election and compare that poll average to the actual election results, we get:

The “Difference” measure is the election result minus the polling average. What we see is that the only case where the election result was substantially lower than the polling average was in the case of the last Federal election – which also happens to be the only example of an Opposition having a large, consistent polling lead anywhere in the country in the last decade or so.

So, did the Labor Party in 2007 have their large polling lead reduced to a small election victory because of the magic of federal political history, a magic that doesn’t exist at the state level – or did it occur because they were an Opposition without the campaign benefits of incumbency to keep the last minute swingers?

On the one hand, recent election history suggests that every government that enjoys consistently large polling leads ends up with a large election victory. Yet, on the other hand, longer term federal election history – as Antony pointed out – suggests that these large election results never or rarely happen. Which one is or will be ultimately correct?

My honest answer is “I don’t know” – which is why I’m completely open minded about the potential size of any ALP victory this year. Especially since  every one of these governments that ended up with big victories off the back of big polling leads were Labor governments.

On something completely different, Crikey has a readers survey going to help further develop the Nature of Crikey <insert ominous music>. So if you read this place, it would be really appreciated if we could pinch about 5 minutes of your time and know your thoughts on what you like or don’t about Crikey and what you’d like to see more or less of.You can even win stuff.