The Greens did two things. First, they decisively won the battle with Labor in inner-city Sydney by clearly winning both Balmain and the new seat of Newtown. They held Balmain against a very strong challenge by the highly-regarded former member Verity Firth and they won Newtown despite Labor fielding an excellent candidate in Penny Sharpe, a sitting member of the Legislative Council.

In other words Labor, desperate to snuff out the Greens in inner-Sydney, threw everything into the contest. But the Greens not only consolidated but expanded their position. The major parties are on the outer in the inner-city if independent Alex Greenwich is taken into account in the neighbouring electorate of Sydney, formerly held by Clover Moore.

Secondly, the Greens had remarkable success against the Nationals in apparently very different circumstances far away on the far North Coast. The swings against the Nationals in Ballina and Lismore were more than 20 per cent, and the Greens have won Ballina and gone close in Lismore. This was a break-out for the Greens much like the inner-city breakouts of the past decade in Sydney and Melbourne.

It came about in large part because of anti-coal seam gas protest being translated into electoral politics. But challenges to the Nationals in this part of NSW are not new in both federal and state politics. Demographic change means that this is not guaranteed Nationals territory.

Perhaps these two "exotic" parts of the state are not so different after all. Demographic change and divisive political issues have shaken traditional party loyalties in both places. Both clusters of electorates feel neglected by the overwhelming desire of the major parties to cater to the comfortable middle ground of the NSW community.

These changes will have broader implications if the Greens' consolidation turns out to be solid and long term. But the alternative interpretation should be noted first. These clusters of seats are still only less than 10 per cent of the whole Legislative Assembly. State-wide the Greens' share of the vote virtually stood still at about 10 per cent. While the inner-city pattern is now well- established it remains to be seen whether major party "sanity" can be restored on the far North Coast once, and if, the coal seam gas issue is sorted out.

Perhaps it is just an electoral blip. But I don't think so. For some time the Greens have had a critical mass of parliamentarians around Australia and this continues to build. In NSW the Greens now have eight MPs, including a better balance between the lower house (3) and the upper house (5). Such a number, backed by staff resources, inevitably contributes to them being able to make a louder contribution, even though they will be locked out of direct policy negotiations by the numbers in both houses.

The party, despite overlaps with other parties, is distinctive in a number of ways which are either accepted or rejected by the wider community. They pose an electoral and ideological challenge to these other parties, especially Labor.

Four distinct elements make the Greens stand out. They are a community-based party coming out of a protest tradition. They are accepted as a party with established environmental credentials. They are the most secular party among the bigger parties and therefore offer a distinctive pro-same sex marriage and pro-euthanasia voice. They are regarded, however, by many Australians as either naively unrealistic or dangerously extremist and therefore not acceptable to them as a mainstream party.

Labor's relationship with its Green "cousins" is one key to the latter's future. It determinedly battles the Greens for two main reasons. First they are direct competitors for the same voters. It is largely a zero-sum game in which one advances at the other's expense. That's not wholly true because each has some distinctive appeal to centre-right voters, but it is largely the case.

Secondly, Labor fears that any association with the "idealistic and/or extremist" Greens tarnishes its image with centrist and rural voters. Therefore they must not just fight the Greens but distance themselves from that party. This fear survives despite regular governing arrangements between the two, including in the ACT and in the former Gillard government.

So Labor faces a problem that the Liberals don't face with the Nationals. The Liberals would rather the Nationals didn't exist, because life would then be far less complicated, but they don't fear much, if any, voter backlash because of the traditional relationship.

The growth of the Greens in NSW, together with two independents, means that it is possible that NSW will return to minority government in 20 19. Mike Baird has a comfortable margin over Luke Foley but it becomes much slimmer if the five non-major party seats are taken into account. An improved Labor performance could quite easily mean reliance by either major party on some combination of these five.

More broadly, if the Greens do become indisputably part of the electoral furniture emporium and not some op shop alternative then the Labor-Green relationship must be confronted head on. Labor's fears won't easily dissipate and the relationship may continue to be fractious. But, even if it takes decades, one day it will become as unremarkable as the Liberal-National partnership.

However, as some Nationals will tell the Greens, marriage is not all plain sailing and should perhaps be resisted. But that is another story.

John Warhurst is an emeritus professor of political science at the Australian National University.

John.Warhurst@anu.edu.au