The Turnbull government would seize a rare, absolute majority in the Senate if it finalises a deal on voting reform and calls a double-dissolution election, according to two experts on the preference system.
The Greens - who are negotiating with the Coalition to end "preference harvesting" among minor parties - would likely lose two of its current 10 senators if it agrees to support reforms and both houses of Parliament are dissolved.
Explainer: double dissolution elections
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Explainer: double dissolution elections
Double dissolution elections can be called early, but they can also radically change the make up of the Senate, explains Chris Hammer.
A review of voting data by Graham Askey and Peter Breen, veteran players in minor party preference negotiations, forecasts the Coalition would win 40 Senate seats - a gain of seven - while Labor would remain anchored at 25 under the proposed changes being sought by the government.
Nick Xenophon, who is pushing to abolish the group voting ticket - the mechanism that allows minor parties to transform a tiny primary vote into seats in the Senate through preference deals - would be the biggest winner, with two new senators joining him in Parliament, according to their projections.
Overall, the Coalition would have a two seat majority and would not have to negotiate with any other parties. The last time that happened, the Howard government passed the controversial Workchoices laws before being punted from office in 2007.
Malcolm Turnbull's retiring deputy Warren Truss had advocated a snap double dissolution election to clear out a problematic crossbench but the Prime Minister has given little sign that he is considering anything other than going full term.
Mr Askey, who previously negotiated preferences for the HEMP Party but has recently joined the fledgling Renewable Energy Party, founded by Mr Breen, said the Greens had not properly considered the ramifications of a double dissolution once voting reforms are passed.
"They haven't done their due diligence. They are walking into this with their eyes wide shut," he said.
"I can't see why Lee Rhiannon [who is leading voting reform negotiations for the Greens] said she would sign up to a deal unless she is the Coalition's Manchurian candidate."
Mr Askey and Mr Breen's review forecasts the Greens would lose one of their two senators in both Western Australia and South Australia in a double dissolution. That would mean the loss of either Scott Ludlam or Rachel Siewert from WA and either Sarah Hanson-Young or Robert Simms in SA, depending on who gets first spot on the Greens ticket.
Senator Rhiannon did not dispute their findings but said her party was committed to voting reform over "electoral advantage".
The Greens are due to meet Mr Cormann again next week amid gathering speculation the government wants to have legislation introduced within weeks.
"The Greens have had a long-standing position in favour of Senate voting reform. In a democracy the outcome of an election should reflect the will of the voters. The current system doesn't do that," Senator Rhiannon said.
"Our work for Senate voting reform is not about trying to secure any electoral advantage. We don't expect it to make much difference to our results.
The end of the group voting ticket - most likely in favour of allowing voters to choose six preferences 'above the line' - would likely wipe out the entire existing crossbench with the exception of Senator Xenophon and lock out minor parties into the future.
Mr Askey said 70 per cent of micro parties are currently right-leaning and have generally taken votes from the Coalition rather than parties of the left.
Once reforms are passed, he said, the Turnbull government and future Coalition governments would have the option of trimming the Greens back to 8 by calling a double dissolution.
"Under any system of proportional preferential voting the Greens will always find it harder to elect two senators at a double dissolution than to elect one at a normal half Senate election," Mr Askey said.
The Greens generally poll about 0.8 of a senate quota in each state but in a double dissolution their second candidate is left with 0.37 and unlikely to get elected on preferences.
Mr Breen, who is a former adviser to Ricky Muir, met with Greens leader Richard Di Natale in Melbourne a fortnight ago to explain the potential negatives for the party.
Projected Senate composition in a double dissolution election
- NSW Coalition 7, ALP 4, Greens 1
- Vic Coalition 6, ALP 4, Greens 2
- Qld Coalition 7, ALP 4, Greens 1
- WA Coalition 7, ALP 4, Greens 1
- Tas Coalition 6, ALP 4, Greens 2
- SA Coalition 5, ALP 3, Greens 1, Xenophon 3
- ACT Coalition 1, ALP 1
- NT Coalition 1, ALP 1
- Total: Coalition 40, ALP 25, Greens 8, Xenophon 3