ACT election 2020: Greens leader Shane Rattenbury on political power in the ACT

In the mind of ACT Greens leader Shane Rattenbury, Canberra's light rail simply would not have been built had it not been for the persistence and persuasion of his party.

Labor mightn't entirely agree with his account of history, but Mr Rattenbury insists those bright red carriages wouldn't be rolling along Northbourne Avenue en route to Gungahlin had the Greens not been pushing to get the long and much talked-about project across the line.

Mr Rattenbury speaks about climate and gaming policy in the same manner. In each case, he says the Greens have been able to leverage their kingmaker position in the ACT Legislative Assembly to push an at times reluctant coalition partner to adopt more progressive policies.

As the 2020 election campaign nears, the Greens are again hoping to snare enough seats - two will probably suffice - to resume their now familiar position as the holders of the balance of power in ACT politics.

The party's more than 10 years as the Assembly's powerful middle force have changed Canberra demonstrably. But has it been for the better? Could the Greens have done more, particularly in areas such as housing and corrections - two of the areas their party leader has had ministerial responsibility for?

And why hasn't Mr Rattenbury threatened the "nuclear option" - blowing up the government - to force it to fold on policies a Green party should not be prepared to accept?

In the function room of the ACT Legislative Assembly on Monday morning, Mr Rattenbury and Labor Chief Minister Andrew Barr happily posed for photos together after releasing the final status update on their latest parliamentary agreement, the 16-page document which sets the terms of the territory's most powerful political marriage.

It is, at least for now, a relatively happy and productive union.

About 80 per cent of the proposals inked in the Labor-Greens power sharing agreement after the 2016 election were achieved during the term, including reaching a long-planned 100 per cent renewable energy target, establishing an integrity commission and delivering light rail's first stage.

The other proposals, including an expansion of the lobbyist register and a review of the energy efficiency rating scheme, weren't delivered, to the mild disappointment of the Greens.

The results were broadly representative of how Mr Barr and Mr Rattenbury publicly portray the parties' relationship - mostly harmonious, but not quite perfect.

The local branches of the two parties appear to have more in common than they don't, and have more to gain from being together than they would apart.

"Our two parties have formed a very effective alliance in this parliament. We don't agree on everything and we are upfront about that," Mr Barr said.

"They say politics is the art of compromise - it is - but when you have a degree of shared values, which the parties do, then you can work together."

The Greens have claimed credit for more than 20 policies or projects delivered by the Labor-dominated ACT government in the past 12 years, including holding Australia's first pill testing trial, establishing the drug and alcohol court and spearheading what they claim to be nation-leading freedom of information laws.

For Mr Rattenbury, the most significant and enduring policy was one written into the Greens' parliamentary agreement with Jon Stanhope's Labor government after the 2008 election. With four MLAs elected to the Assembly benches, the Greens pushed for a legislated greenhouse gas emissions target.

The nailing down of that target, which now aims for net zero emissions by 2045, set the foundations for the ACT's acclaimed climate policies, including the reverse-auction green energy investment scheme.

After a term in the Speaker's chair, Mr Rattenbury has for the past eight years been the sole Green in a Labor cabinet, holding 11 separate portfolios including justice, education, housing and climate change.

That position has given him, and the ACT Greens, the power to determine government policy in some areas, and at least have their voice heard directly on others. It is a level of influence no other state branch of the Australian Greens currently has (Labor and the Greens governed together for a number of terms in Tasmania, and were in an alliance federally under Julia Gillard and Bob Brown).

But for Mr Rattenbury and the ACT Greens, power has a price. The price is responsibility, and consequences.

Mr Rattenbury's position inside the tent means that neither he nor the Greens - and that includes his retiring crossbench colleague Caroline Le Couteur - can fully separate themselves from the Labor government's failures. It is, as the Canberra Liberals are always keen to point out, a Labor-Greens, or Barr-Rattenbury, government which rules in the ACT.

The Greens leader certainly can't absolve himself of responsibility when one of those failures or shortcomings relates to one of his portfolios.

Canberra's prison has been plagued by problems during Mr Rattenbury's two terms as Corrections Minister. Aboriginal incarceration has grown by 279 per cent between 2009 and 2019, the biggest jump in any Australian state and a rate the Greens leader - who was Minister for Aboriginal and Torres Strait Islander Affairs for more than two years - describes as unacceptable.

The Greens list the creation of a dedicated mental health ministry among their proudest achievements, but that portfolio has attracted its own share of problems, including persistent issues surrounding a lack of mental health beds in the ACT.

Mr Rattenbury also served as ACT housing minister for 20 months during a decade in which housing affordability has worsened, overall public housing stock has grown only marginally and wait times for a standard tenancy have blown out beyond 1200 days.

Does he accept responsibility?

"You have to own some of that," Mr Rattenbury said.

"There are things that we have not been able to achieve - that is why you front up for an election."

Mr Rattenbury said Canberra's housing crisis was real, hence why the centrepiece of the Greens' 2020 election policy platform is an ambitious $400 million strategy aimed at tackling housing affordability and homelessness.

In her valedictory speech to the ACT Legislative Assembly on August 27, Ms Le Couteur lauded recent progress on social and environmental issues, while lamenting enduring problems in the territory's planning system and growing income inequality in the nation's capital.

The Greens expose themselves to ridicule whenever they bemoan the government's performance because of their position inside that government.

It does lead to the question of whether the junior coalition partner has used the full weight of their power and leverage to achieve outcomes for the Canberrans they exist to represent.

Mr Rattenbury said he does strongly lobby his Labor cabinet colleagues to advance the Greens' interests - the public just very often doesn't see it.

"We spend a lot of time having quite strong arguments behind doors," he said.

"You come out of an election and you have a result where there isn't a majority government. You have a duty where the government needs to work for the next four years. We are not here to be wreckers, we are here to get things done.

"A lot of the disputation is not necessarily publicly played out. Some politics might suggest we should do it more visibly. But to have a working relationship you've got to seek to collaborate where you can."

Under the power sharing deal, the Greens guarantee supply of the government's budget bills and commit to not supporting a motion of no confidence in a minister unless they have been found guilty of corruption or gross negligence.

But the Greens do always have in their back pocket that "nuclear option" - the ultimate power play which could bring the government to its knees.

So why don't Rattenbury's Greens use, or threaten to use, this power? Firstly, he doesn't believe Labor has done anything to warrant such extreme action. And would it actually achieve anything?

"People often say you have a lot of power ... and they ask about why we don't exert it," he said.

"One needs to understand the political context. There is a suite of options ranging from what you might describe as a nuclear option - felling the government - through to at the other end of spectrum where there is cajoling, arguing and persuading.

"There is actually not a lot in between."

While it has its fair share of critics inside the ACT, the Labor-Greens coalition has been held up as blueprint for how power sharing can lead to policy outcomes.

Ben Oquist, executive director of Canberra-based think tank the Australia Institute, worked for more than 10 years alongside Greens elder Bob Brown, including in the term in which he propped up Julia Gillard's federal Labor government.

Mr Oquist said the Hare-Clarke proportional representation system, which has delivered just one majority government in the ACT in more than 30 years, meant that Canberra's political parties had to be able to co-operate.

"I think that can produce better outcomes," he said. "It tends to produce not just coalitions of convenience, but it drives a more co-operative style that leads to consensus outcomes."

The Greens' numbers in the ACT Legislative Assembly have fluctuated from four to one to two over the past three terms.

Mr Rattenbury said if the results of the 2019 federal election were replicated at the ACT ballot the Greens could win as many as six seats on October 17.

While a haul that large is extremely unlikely, the Greens are optimistic about claiming at least three seats in the next ACT Legislative Assembly - Mr Rattenbury and Rebecca Vassarotti in the city seat of Kurrajong and Emma Davidson, who is desperately trying to hold on to Ms Le Couteur's spot in the Woden and Weston Creek-based electorate of Murrumbidgee.

The Greens have so far rolled out the most comprehensive election platform of the three major parties, with detailed, costed policies on housing, environment, waterways, flexible employment, drug law reform and electric cars.

The Greens' critics will always dismiss their ambitious and expensive policy proposals as the unrealistic thought bubbles of a party which will never have the responsibility of delivering them.

But Mr Rattenbury said the ACT Greens did aspire to being more than just a powerful third force in territory politics.

He can picture the Greens in opposition, potentially as soon as within the next decade.

And what about the top job?

"I'd love to think there would be a Greens chief minister in Canberra at some point," he said.

"I think we have got the policies and we've now got the experience in government.

"The fact [is] that I've now been able to hold ministerial portfolios for eight years and we've got a series of things that we can point to and say 'when the Greens get the opportunity, we can do it'."