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Rudd, the last one standing?: Federal implications of QLD state election results

Wednesday April 4, 2012

Filed under: Australian Politics,R,statistics — jackman @ 12:40 am

Labor won 15 of Queensland’s 29 House of Reps seats in the 2007 Federal election (AEC details here). Yet just three years later, in the 2010 Federal election, Labor won only 8 of 30 Queensland Reps seats, with 33.6% of 1st preferences (a swing of -9.3 percentage points).

Labor’s best performance on 1st preferences in 2010 was in Capricornia (46%), which translated into a 54-46 2PP result. Kevin Rudd won Griffith with 44% of 1st preferences, resulting in a 58-42 2PP result. Wayne Swan and the LNP candidate split the 1st preferences in Lilley, 41-41, with Swan winning the seat with Green preferences, 53-47 2PP. Labor managed to get home in Moreton in 2010, with 36% of the 1st preference vote, and a 51-49 2PP result.

The state election of some 10 days ago was conducted under different district boundaries (89 seats in the Queensland parliament) and a different electoral system (optional preferential). Moreover, the Katter Australia Party ran candidates in 76 seats, winning 11.5% of 1st preferences, further complicating comparisons with previous elections (state or federal). In any event, Labor won about 26.7% of 1st preferences (ECQ results), down 6.9 percentage points from its performance in the 2010 Federal election, and down a staggering 15.6 percentage points from the 2009 state election.

How might these 2012 state-level results translate into Federal results?

There are many different ways of looking at this, all of which involve a little guesswork and assumptions given the differences in the two electoral systems, the configuration of parties and so on.

Here’s a stab that I’ve been working on over the last week or so (“Spring Break” here at Stanford). The AEC conveniently (!) geo-codes its polling places and publishes that data on its web site. Shape files for Federal electorates are also available. This makes it feasible to start re-aggregating booth-level results from the state election up to Federal seats.

A few steps and assumptions are required (and I’ll write this up at some point):

So what do you get when do this re-aggregation, subject to all the caveats sounded above? Keep in mind I only have 1st preferences, at least for now.

The figure below (click for full-size) shows a scatterplot of imputed Federal results for the ALP given the 2012 state results, for each of Queensland’s 30 Federal seats, against the ALP’s actual 1st preference vote share (%) recorded in the 2010 Federal election. The diagonal line is a 45 degree line, a “no difference” line. On average, the data points lie below the diagonal, indicating what we know, that Labor did considerably better in the 2010 Federal election than in the 2012 state election.

Red dots and labels indicate the 8 seats won by Labor in 2010. The good news (!?) for Labor is that the Federal seats in which its primary vote utterly cratered are seats in which it had no chance of winning in the 1st place, where its 2010 1st preference vote share was below 30% or barely above 30% (e.g., Wide Bay, Maranoa, Fairfax, Wright, Fisher, Hinkler).

The bad news for Labor is that it would seem that most of its 8 Federal, Queensland seats are at some peril, with the exceptions perhaps being Griffith (Rudd’s seat), and maybe Rankin (Craig Emerson) and Oxley. The estimated ALP 1st preference vote share given the 2012 state results in these 3 seats lies above the actual ALP 1st preference recorded in Moreton in 2010, which was Labor’s weakest among the 8 seats it won in 2010 (and observe the many assumptions implied in that extrapolation).

Lilley — Swan’s seat — will be interesting. I grew up in Lilley on Brisbane’s northside. When Labor is really on the nose, it goes to the Coalition. Swan lost the seat in 1996 in his sophomore election, but has held it since 1998. I’m not sure the last redistribution helped, and its tough to see Labor win it if its primary vote share slips below 35%. Complicating factors are what role might the Katter party play, as well as some kind of “personal vote” for Swan (an incumbent Federal Treasurer, no less).

I also show the implied swings given by these estimates of ALP 1st preference vote share (bigger version available by clicking):

This presentation of the data highlights that Griffith (Rudd’s seat) has the smallest implied swing among Labor’s 8 seats, around about 5 percentage points. Coupled with the fact that Rudd starts off at a tolerable level of 1st preference support, this bolsters confidence that Griffith remains Labor’s best shot at a “retain” in 2013.

The implied swing in Moreton is only a little larger, but there is far less buffer there. Swings of -7 to -8 percentage points on 1st preferences in Lilley, Rankin and Oxley would have to be almost surely fatal to Labor’s chances there. And double digit swings in Petrie, Blair and Capricornia would also have be beyond the margin of survival.

Could Rudd be the last (QLD, Labor) one standing?

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