No other minor party has achieved this. The Australian Democrats came close with nine senators at one time (after being on the political landscape for 21 years) but the Greens are now the third force in Australian politics. The Greens will hold the balance of power in the Senate in their own right and may play a critical role in determining government in the lower house. I notice the Prime Minister did not rule out ministerial offers yesterday. Potentially, this result is thrilling for progressive politics and for those who believe in multiparty democracy. But many voters - including those who voted Green - are wondering if the Greens are ready for power or just for protest. There are plenty of things the Greens have done right to get where they are.

They've enjoyed consistent leadership: Bob Brown has seen off four Liberal leaders, five Labor leaders, even five Democrat leaders (mind you, Brown was the only Greens MP for several years). They've had few public internal ructions and have faced minimal media examination. The party has worked hard to develop a strong grassroots membership and run candidates for all tiers of government. Equipped with $4 million in public funding from the 2007 election and a record $350,000 donation from the Electrical Trades Union, the party produced effective paid advertisements and used the internet better than other parties. The Greens capitalised on the government's failure to act on climate change and its lurch to the right on asylum seeker policy, thus attracting disenchanted left-leaning Labor voters. However, a sizeable chunk of the Greens vote was a protest. Voters were disillusioned with the risk-averse and scripted style of the major parties, and sought viable alternatives of which there were few, evidenced by the jump in informal votes.

The Greens are canny enough to realise they were beneficiaries of this "pox on both your houses" sentiment, but this means some voters are unaware of the Greens' policies. This presents a challenge in that a proportion of their constituents may be more centrist than the party's MPs or their grassroots members. The Greens will also face the challenge of maintaining a participatory democratic framework for their membership while ensuring they facilitate legislation in the Senate in a timely and methodical way. The problem with the smallness of minor parties is that personality clashes and opinion differences often seemed magnified, especially in the media spotlight. Already, some are speculating about succession in the Greens: What happens when Brown retires? And what factional and geographic issues will come to the fore as a result? Yesterday, Brown did not look like he had any intention of leaving as he talked up the party's willingness to negotiate and its economic literacy. He and his tyro senators will need to make sure they can back this up, especially when debating the mining tax, company tax issues and trade with China.

The Greens' role in determining who may govern is now being dissected. Bandt's stated Labor preference was picked over by the media yesterday, as his leader dampened such impressions. Much of the Greens' policy and legislative work is in its early stages. Some of it echoes that of other parties such as the Democrats (particularly on accountability matters and when it comes to private member's bills) and their negotiations (including on the stimulus package) conducted in the context of the shared balance of power. The Greens have the opportunity to influence and initiate policy and they will have to avoid the temptation to cross-trade on legislation. They don't necessarily have to sacrifice their activist work outside Parliament for productive work inside, but it is not possible to simply be a party of protest in Parliament, especially when the balance of power comes into play. Crossbench senators have to get their hands dirty with the nitty-gritty of legislating, committee work, meetings, negotiations and compromise (although not on values).

It is an exciting opportunity and, judging by the look on Brown's face, one that he's been waiting a long time for. Despite attempts by some shock jocks to spook voters about the Greens' policies (closing down zoos or reintroducing death taxes), it is more likely the Greens - with Senator Nick Xenophon - will provide an important check on executive power. Given the workload and resources, it may not always be easy being Green in the next Parliament. Natasha Stott Despoja is a former leader of the Australian Democrats.