The defeat of the Rudd government’s Emissions Trading Scheme (ETS) in the Senate last week achieved the first of two parliamentary rejections of the enabling legislation that could become the basis for a double dissolution election.

If Malcolm Turnbull’s Liberal-National coalition were to reject the bills again in November, Mr Rudd would have the reason he would need to ask the Governor General to invoke Section 57 of the Constitution and call fresh parliamentary elections.

A double dissolution election involves the dissolving of both the House of Representatives and the Senate in their entirety.

In a normal election, all of the House of Representatives and half of the Senate are up for election, so the need to fill all 76 Senate seats in a double dissolution election has important consequences for the vote a candidate needs to win to secure a position in the upper house.

In a half Senate election, a candidate needs to win 14.4 percent, whereas in a full Senate election, the vote required is around 7.7 percent.

It is this reduction in the vote a candidate needs to win to secure a seat that is the important point to grasp. In a full Senate election, the reduced electoral threshold means that minor party candidates and even independents have a much greater chance of securing a seat than they would have in a half-Senate contest.

As things stand at the moment, a full Senate election would probably see at least one Green candidate returned in every state.

The exception to this would be Tasmania, where both sitting senators Bob Brown and Christine Milne would be up for election.

Both are sufficiently popular in their home state to secure a seat each. This would leave the Greens holding up to seven seats.

There is not a great deal of mutual affection between the Greens and the ALP, but a Senate outcome in which the Greens held the balance of power in their own right would suit Mr Rudd.

The prime minister would have to deal with the cross-benches to get his government’s legislation through, but at least he would have to deal with only one group of cross-bench Senators.

At the moment, Rudd has to deal with three groups, including the Greens, Family First and the South Australian independent, Nick Xenophon.

The problem for Mr Rudd, should he seek a double dissolution, however, is that he might end up with exactly the same difficult Senate that he has been trying to deal with since his election in 2007.

A double dissolution would force Xenophon back to the polls, where his popularity has been demonstrated to be strong enough to win enough votes to secure a position for himself and, possibly, a second candidate on his ticket.

Meanwhile, in Victoria, a double dissolution might be the outcome that saves the Senate career of Family First’s Steve Fielding.

He was the senator who won a seat in 2004 with less than 2 percent of the primary vote. Fielding got in last time because of Labor preferences.

Labor won’t be directing its preferences to Fielding next time and, were the next contest to be a half Senate election, it would be almost impossible for Family First to secure a seat.

A full senate contest greatly enhances his chances, however, especially if he were to receive preferences from the Liberal and National parties, an outcome that seems very likely indeed.

All this means that it is possible that a double dissolution election could result in a Senate that becomes even more difficult for the next government to manage.

This compares with the possible outcome of a normal half-Senate contest.

In a half-Senate election, Xenophon would not be up for re-election and Fielding would fail to win a seat.

The Greens, too, would be assured of winning only one seat in Tasmania.

In the other states, a Green success would be by no means guaranteed and would depend heavily on a favourable flow of Labor preferences.

The Coalition would also lose ground as it would surrender the extra seat it won in Queensland in 2004.

In short, the prospect of Mr Rudd being able to manage the Senate more effectively than he does now is much greater under a half-Senate election than a full Senate election.

It will be interesting to see if these strategic considerations influence Mr Rudd’s decision to seek a double dissolution should the Coalition defeat the ETS for a second time in November.

Dr Economou is a senior lecturer in Politics at Monash University.