In the century since Australia’s two-party system became established, 17 state or federal governments have sought re-election for a fifth term.
Queensland’s Labor government this month becomes the 18th (see the UWA database for complete results).

Of those 17, 11 were successful and six were defeated, a success rate of 65% — only fractionally worse than the re-election rate for governments in general, 154 out of 232. It also seems to make little difference whether they were Labor or non-Labor governments (63% and 67%, respectively). So does that mean a government is no more vulnerable after four terms than at any other time?

Not so fast. If we break the figures down chronologically, a different picture emerges. In the first 33 years (1909-41), every four-term government was re-elected (admittedly there were only three of them). From 1942 to 1974, seven out of nine were successful. But of the five cases since 1975, only one has been re-elected: the federal Labor government in 1993.

Four-term Labor governments have been defeated in New South Wales (1988) and South Australia (1979), and non-Labor governments in New South Wales (1976) and federally (2007). Apart from Queensland, the other current four-term government is in New South Wales, and its defeat is almost universally expected in 2011.

Something seems to have changed in how Australian voters view longevity of government. On the one hand, re-election rates for first term governments have skyrocketed, from 50% in the early period to 86% recently. But this tolerance for new governments is matched by an increasing impatience with those that have been around longer.

Back in 2005, Peter Brent argued that “re-election just gets harder” over time: “As a government gets older, the ‘neutral position’ goes from there being no reason to change to there being no reason not to.” I used to be sceptical of this argument, but it’s looking better and better, and if Anna Bligh’s government goes down on the 21st it will be strikingly confirmed.

Long-serving governments always amount to a fairly small sample, so it’s possible the variation is just statistical chance. But it does look as if holding on to voter allegiance is getting harder, and Labor in Queensland is fighting against the trend.