The senate is to change: Will Australian politics change to?

The Australian Constitution is full of oddities, and the rules relating to the Senate are no exception. At federation, the idea was that the Senate would represent the Australian states and would be kept some distance from the powers of the government of the day whose authority would be derived from its majority in the House of Representatives.

Thus senators would have six year terms, the constitution would prescribe the minimum amount of time that would have to elapse before a half-Senate election could be called, and the term of the Senate would have a different commencement time than the lower house. As a consequence, something very important to Australian politics occurs on 1 July. According to the Constitution, those men and women elected to the Senate in the 2010 election will at last be able to claim their seats in the upper house and replace those senators who were elected all the way back in 2004.

The most immediate impact of this change will be to alter the so-called 'balance of power' in the upper house. For the last three years a politically diverse collection of senators including Greens, Family First's Steve Fielding and the independent South Australian Nick Xenophon have been the power-brokers in the upper house. Indeed, since the election of Labor back in 2007 and with the Greens tending to support Labor more often than not, it has actually been Fielding and Xenophon whose votes have determined everything from procedural outcomes to actual policy.

Xenophon in particular has used this politically important situation to project himself on to the political debate, as the federal government's consideration of legislation to restrict the use of electronic gaming machines has indicated. After 1 July, however, Senator Xenophon will no longer be in such a powerful position to bargain for his vote, and Steve Fielding will have left the chamber altogether. In their place will emerge the new powerful force in Senate politics - the Australian Greens. While much commentator attention about the Greens has concentrated on lower house MP Adam Bandt and his historic election as the member for Melbourne, it could be argued that the more significant advance for the Greens has been occurring in the Senate.

Over a succession of elections the Greens have gradually increased in number in the upper house. The 2010 election was arguably the party's best election so far, with Greens being elected in each state. From 1 July, the Greens, with nine senators, will hold the balance of power. It is not immediately clear as to what this is going to mean for the national policy debate over the next two years, after which a federal election becomes due.

In one sense the impact of the Greens has already been felt with Labor Prime Minister Julia Gillard clearly of the view that, in order for her minority government to survive, she had better align herself with the Greens' policy of instituting a carbon tax. The two parties are currently negotiating over just what the price of carbon should be, although, if the polls are any guide, Gillard and her colleagues have sustained some serious political damage as a result of reneging on a campaign promise to not institute such a tax. The rate at which carbon is proposed to be taxed will give an indication of what the Labor-Green dynamic is likely to be over the course of the rest of the government's tenure. An outcome closer to the government's flagged rate of around $20 per tonne would indicate that the Greens under the leadership of Senator Bob Brown will be prepared to be flexible and pragmatic.

A price closer to $40 or more would simply confirm that the Greens, rather than Labor, are now running the climate change debate. It's doubtful that the Gillard government could sustain such an outcome. Gillard's chances of being re-elected really depend on Brown being able to keep his parliamentary Greens committed to a more moderate approach to the policy debate. The imperative is less urgent for the Greens, however.

The nature of the Senate electoral system is such that at least six of the current nine Greens will remain in parliament until 2016. The Greens would win at least one seat at the next election, although the more likely scenario is that the party could win another six seats to bring the party's total presence to 12! The really interesting thing here is that it is conceivable that Tony Abbott and the Liberal-National coalition will win the next federal election.

This would leave the coalition prime minister in the unenviable situation of having an ideologically hostile Senate - the first time such a situation would have arisen since the period between 1972 and 1975 when Labor's Gough Whitlam faced a Senate controlled by the Coalition. For those who have forgotten, governments facing ideologically opposed upper houses can find survival, let alone policy-making, something of a major struggle. Whatever the future brings, the national political debate had better get used to the Greens being a major presence in the Senate, for this could be a situation that will endure for some time. Dr Nick Economou is a Senior Lecturer in the School of Political and Social Inquiry at Monash University.