Voters in Western Australia look certain to be headed back to the polls for a re-run of the botched Senate election, after yesterday’s determination by Justice Kenneth Hayne that “the only relief appropriate” was to vacate the original result.

Hayne’s ruling also made it clear that a new election would proceed in the conventional manner, with all six seats up for grabs and a new nominations process open to all comers — including any micro-party chancer hoping to follow in the well-publicised footsteps of Ricky Muir and the Motoring Enthusiasts Party, regardless of whether they have any actual connection to the state they aspire to represent.

The decision is particularly unwelcome for the Liberals, whose court submission was a tour de force in support of any solution that didn’t involve a fresh election.

The Abbott government must now brace itself for a super-sized byelection involving one in 10 of the nation’s voters, who have a no-strings-attached opportunity to give vent to the dissatisfaction that has been coming through in the polls recently — not least in Western Australia, where the trend points to an anti-government swing of over 6% off the high base of the September election result.

Should that translate at the ballot box, the new election could prove a win-win for Greens Senator Scott Ludlam and Labor’s Louise Pratt, one of whom was to have been left holding the bag when the original result reduced the “Left” parties to two seats out of six.

A statewide byelection also promises to play to the advantage of the Palmer United Party, which will have the luxury of concentrating its formidable advertising firepower on a single state.

If the pendulum indeed swings far enough to deliver a third seat to the Left, any win for the PUP would have to be at the expense of one of the Liberals’ three seats.

Promising as all that may be as a source of political theatre, the effects on the Senate balance of power are likely to be rather subtle. The government will in any case need support from the Palmer bloc to win the day if Labor and the Greens line up against it, along with extra votes from a crossbench encompassing Nick Xenophon, David Leyonhjelm of the Liberal Democratic Party, Bob Day of Family First and John Madigan of the Democratic Labor Party (taking Ricky Muir to be aligned with the PUP).

While none of the four can be identified with the Left, they are in their own way an intriguingly eclectic mix: two social conservatives in Day and Madigan, the stoutly libertarian Leyonhjelm, and a wild card in Xenophon, who made his name as an anti-pokies crusader but generally seems rather mercurial in his philosophical outlook.

Based on what was initially understood to be the result of the election, the government would only have needed two out of four in addition to the Palmer bloc. If Labor and the Greens win an extra seat, that becomes three out of four.

Apart from the candidates directly affected, it’s largely academic whether the third “Right” seat goes to the Liberals or the PUP, as the support of the latter will be required in any case — something Palmer isn’t likely to let the government forget in a hurry.