After both the 1983 and 1987 double dissolutions, the six-year terms were granted to those senators who received the highest number of votes.

But, as an alternative there is the countback provision. Under this, each elected senator would be ranked as if it was a half-Senate election, and their vote matched against the much higher quota for a seat of 14.28 per cent.

The Senate would be recounted on this basis and it would overwhelmingly favour the major parties.

For example, in Queensland, the top six spots would be filled by three Liberal-National Party Senators and three Labor Senators and they would consequently receive six-year terms. Ms Hanson won 1.2 quotas in the double dissolution but under the countback system, this would rate as just over half a quota in a half-Senate election and she would be relegated to the bottom six. Similarly, Queensland Greens Senator Larissa Waters who won a full quota in the double dissolution, would be relegated to a three-year term.

In South Australia, Senator Nick Xenophon would make the top six based on the sheer size of the NXT vote but the other NXT Senators expected to be elected on his ticket in South Australia would be bottom six, meaning he could again be a lone voice following the 2019 election.

AAP photo. DO NOT USE after 4 July 2016. One Nation's Pauline Hanson takes questions from the media during a news conference in Brisbane, Monday, July 4, 2016. The One Nation leader believes her party could win two Senate seats seats in Queensland, one seat in NSW and Western Australia and possibly one in each of Tasmania and South Australia. While Malcolm Turnbull and Bill Shorten have been phoning key crossbenchers about their support for a possible minority government, neither has spoken to Ms Hanson. (AAP Image/Dan Peled) NO ARCHIVING . DAN PELED, AAP

Act of goodwill

The Constitution only says that after a double dissolution, half the senators must receive six years and the other half three. It is silent on the mechanism.


It is up to the 76-member Senate to choose the mechanism and Labor and the Coalition will still easily have a combined majority, despite the Coalition being expected to lose two Senators.

Sources said both major parties have "turned their minds to the question" of invoking the countback mechanism.

Liberal Senate leader George Brandis said on Monday he had endeavoured to contact Ms Hanson and other newly elected Senators as an act of goodwill. He said all had been legitimately elected and that must be respected, regardless of their ideology or other views..

Ms Hanson used a fiery opening press conference to lay out her demands which included a royal commission into Islam.