Shane Rattenbury's partnership with ACT Labor will be closely scrutinised. Photo: Rohan Thomson
What sort of political animal is the Labor-Green arrangement in the ACT?
Opposition Leader Zed Seselja reckons it is a coalition and, while not strictly correct, he is not too far from the truth. A coalition is a formal arrangement between parties in government (and occasionally in opposition too). This is actually one step from the ACT situation in which Shane Rattenbury has accepted a ministry under certain conditions just as the Greens have done in Tasmania. One MP doesn't really make a Coalition partner.
But it is close to a coalition. It is closer than the current agreement at the federal level where the four MPs support the Gillard government without any one of them entering the government per se.
Seselja uses the term coalition with specific intent. He wants to emphasis the closeness of the Labor-Green relationship. He hopes that this will rebound on both Labor and the Greens, the former for giving away too much and the latter for acting above their station given the swing against them at the election.
Yet the Liberal and National parties at the federal level glory in the term and would not accept that it is a term of abuse. They are known as the Coalition and with a couple of small interruptions have been so for many years. They enter elections as a Coalition and remain in Coalition even in Opposition.
What's the difference?
Coalitions are very common in Europe. Even Britain is now governed by a Conservative-Liberal Democrat Coalition. In every coalition there is a senior partner and one or more junior partners. The relationship between the senior and junior partners includes two possibilities. One is that the junior partner gets more than its due out of the relationship. This is known as ''the tail wagging the dog'' syndrome.
Those who reckon that Rattenbury, the so-called Mayor of Canberra in his new ministry, has too much power think this is a good description of what is happening locally. In this version the Greens have ''greened'' the Labor government.
A similar allegation was made recently in federal politics when the Opposition opposed the Gillard government's liberalisation of wheat marketing. This distressed some Liberals, a couple of whom abstained, thus allowing the government legislation to pass.
Critics alleged that this was an example of the junior Nationals, traditionally more protectionist than the Liberals, manipulating their senior-partner Liberals. You could call this by analogy the ''browning' of the Liberals within the Coalition.
Generally major parties object to such a perception and resist the idea of the tail wagging the dog.
ACT Labor has been very concerned to argue that the introduction of light rail (the centre-piece of the Labor-Green agreement) is actually their idea not the Greens. In fact it is a shared idea.
This points the way to another, contrary interpretation of coalitions. Let's call it the ''tiger by the tail'' interpretation.
Generally speaking it is the junior partner who has the bigger problem. They are the ones who are taken for granted and become submerged in the larger entity to their detriment. The tiger is the major partner. The junior partner is along for the ride but rather than being a jockey steering they are just hanging on for dear life.
They have no control.
Just look at the Liberal Democrats in Britain. They have been taken to the cleaners by the Conservatives and forced to go along with policies at odds with their beliefs. Voters have deserted them in local government elections and they run the risk of being slaughtered at the next British election.
With the federal Nationals this is a recurrent problem. They must justify their participation in the Coalition to their own supporters. While they claim that the ministries, including the post of Deputy Prime Minister, they are given means that the deal with the Liberals is well worthwhile they find this hard to prove.
As a consequence the Nationals have a big identity problem.
The Rattenbury experiment will be watched not just by ACT voters but by Greens all around Australia. If the long-term future of Labor-Green relations is to be some form of alliance then it is very important how this one works out.
One test will come at the next ACT election and another will be the policy outcomes of the government. This is not to say that the Greens are already a left version of the Nationals in parliamentary terms. The Greens have yet to show that outside proportional representation systems - including the Senate, Tasmania and the ACT - they can regularly win seats.
Their support is spread more widely but also more thinly than the Nationals. It is the concentration of voters that enables the Nationals to win lower house seats. Single member electorates really test the level of Greens support.
One scenario is that the Greens might become the party of the left in inner-city metropolitan Australia. If they could regularly win four or five seats in federal parliament and/or state parliaments, such as NSW and Victoria, then Labor-Green coalitions might become more common, though still irregular. We are nowhere near that scenario yet.
Another scenario is that coalitions will be restricted to Tasmania and the ACT. At the federal level the Greens will then be restricted to the more limited, but to some extent more comfortable, role of holding the balance of power in the Senate. That is a more flexible role and comes into play with Labor and Coalition federal governments.
The ACT case suggests that Australian politics is in transition. Watch the outcome carefully.
John Warhurst is an emeritus professor of political science at the Australian National University.