Once upon a time, nearly everybody voted for the major parties. In 1975, after the collapse of the DLP and before the rise of the Democrats, 95.9% gave their primary vote in the House of Representatives to either Labor or the Coalition. That figure was still well above 90% as late as 1987.

Then things started to happen. In 1998, with One Nation, the Democrats and the Greens all in the field, the major party vote fell to 79.6% – the second lowest in history, and the only time it’s been below 80% since 1934. As One Nation dwindled it rose again, reaching 85.5% in 2007, but now it’s back down. On the latest figures (which will change, but only slightly, with postals) Labor has 38.5% and the various components of the Coalition between them have 43.5%, for a total of just 82%.

That’s not the only sign of discontent with the mainstream offerings. The informal vote was 5.6%, up by about a third from 2007 (who knew Mark Latham was so influential?). And within the major parties, there seems to have been a shift toward the mavericks and the unconventional – witness the 11.5% swing to Malcolm Turnbull in Wentworth.

So this looks like a clear movement against machine politics and business-as-usual. Whether however it will be a lasting movement, or just a temporary blip on the scale like 1998, is a different question.

The big difference from 1998 and 2001 is that the minor party vote then was spread among three significant parties. This time, it’s heavily concentrated in the Greens, who with 11.4% have leapt the psychological 10% barrier for the first time – the fourth minor party to ever do so (Lang Labor did it in the 1930s, the Country Party has done it several times and the Democrats did it once, in 1990).

So for all the attention currently being focused on the independents, the future of big party hegemony in Australia for the time being will mostly depend on the Greens. They have before them the bad example of the Democrats, who fell precipitously from their 1990 peak of 11.3% to just 3.8% three years later. If the same thing happens to the Greens, many people in the major parties will breathe a lot easier.

But although their level of support is much the same, the Greens have several advantages over the Democrats. Their support is more concentrated, giving them a power base in the inner cities where they are competing with Labor on a two-party basis. It was rare for the Democrats to ever carry even a single polling place, but there are now a swathe of majority-Greens polling places across inner Melbourne and Sydney, plus a sprinkling of them elsewhere. There are also a number of strong Liberal areas where the Greens are poised to take over from Labor as the second party.

Perhaps more importantly, the Greens have a philosophical coherence to them that the Democrats always seemed to lack. One does not have to agree with the Greens to recognise that they represent a genuine social movement, with activists who actually want to do things rather than just gain power (or just deny it to someone else). That offers some hope that their newly-enlarged caucus will be less prey to destructive personality disputes than the Democrats were.

The Greens also have the advantage of having grown slowly. The Democrats (like One Nation) were an overnight sensation, winning 9.4% in their first election, whereas the Greens have built support gradually over two decades. That gives them a more experienced leadership and a more durable party structure; it should also make them less vulnerable to sudden changes of fortune.

Successful parties needs to stand for something, but they also need to display flexibility. A party that is ideologically bereft risks the fate of the Democrats, but too much ideology can be just as dangerous. The jury is still out on whether the Greens can display the required degree of pragmatism.

For the major parties, however, shortage of pragmatism is the exact opposite of their problem. The electorate is tired of sloganeering, opportunism and focus-group-driven policies. If Labor and the Coalition learn that lesson, they may yet recapture their dominant position. If they don’t, the Greens – or someone else – will fill the vacuum.