SARAH FERGUSON, PRESENTER: In the lead up to Saturday's re-run of the WA Senate election, Labor leader Bill Shorten urged voters to send the Government a message, but it seems voters instead sent one to Labor. The party recorded its lowest primary vote in a Senate election in more than a century and Clive Palmer's Senate bloc now appears likely to share the balance of power in the Upper House from July.

On the Government's part, it says a five per cent drop in its vote since the last election is standard for a by-election result.

Political correspondent Sabra Lane.

TONY ABBOTT, PRIME MINISTER: If you want to see the carbon tax gone and the mining tax gone, the only way to be sure is to vote for the Liberal ticket, it's to vote for a Coalition candidate. ...

... He's out there trying to buy seats in the Parliament and that's something that I don't think the people of Western Australia will fall for.

BARNABY JOYCE, NATIONALS SENATE LEADER: For me, I know this game fairly well after nine years in politics. What you're buying is anarchy.

SABRA LANE, REPORTER: It was an unprecedented re-run of the West Australian Senate election and it's thrown up all sorts of historic results.

Last September, the Liberal Party easily won three Senate seats in the west, but given Saturday's fresh election was held in a different atmosphere, some within the Coalition feared the Liberals wouldn't be able to repeat that electoral performance.

But the ABC's election analyst Antony Green thinks by the time the Australian Electoral Commission officially proclaims the WA result in four weeks' time, the Coalition will claim three new seats, with Labor, the Greens and Palmer United Party all holding a seat each.

ANTONY GREEN, ABC ELECTION ANALAYST: The main story out of the WA Senate election is the disastrous result for Labor. It's the lowest Labor vote in an election - a Senate election since 1903. Their vote went substantially down. The loss of vote for the Liberal Party's what you'd expect at a by-election.

SABRA LANE: For the ALP and its relatively new leader Bill Shorten, the result's a shocker. Mr Shorten urged voters to send the Government a message about planned cuts to health and education. Instead, voters have sent him and the ALP a strong and unmissable missive: they don't like what they see and hear.

The Palmer United Party attracted nearly 12.5 per cent of the vote, with a big swing towards the party of nearly 7.5 per cent. The Greens too recorded more than 15 per cent, and not far ahead them, Labor on 21 per cent of the first preference vote. It will probably win just one seat.

ANTONY GREEN: I think the final spot will be won by the Liberal Party. From this point on, their vote should go up slightly during the count.

DAVID LEYONHJELM, SENATOR-ELECT, LIB DEM PARTY: This has many elements of a by-election - so there's a bit of a protest vote, a bit of an "Up you" to the lot of them, "I hate you all" type of thinking.

GEOFF GALLOP, FORMER WA PREMIER: It's no good pretending that this is just an unfortunate incident that related to a little bit of instability in one election. This sort of instability is now permanent in the structure of the Labor Party as it exists. And if it's going to flourish and prosper, it has to make the big change and the big change has to be to break that link between a couple of unions and the power that they have in the party currently.

SABRA LANE: The former West Australian Labor Premier Geoff Gallop argues the party's facing an existential crisis.

GEOFF GALLOP: Catastrophic. And I think it ought to be a turning point. It ought to be one of those occasions when all of the arguments that have been floating around in recent years about the need to reform the party really come to the surface and the issue's taken seriously.

SABRA LANE: Labor pre-selected the conservative union leader Joe Bullock in its first place on its Senate ticket, ahead of sitting Labor Senator Louise Pratt.

Last week it was revealed the Mr Bullock had given a speech to a Perth audience last year where he admitted he didn't always vote Labor. He described some members as "mad" and questioned the sexuality of Senate running mate Louise Pratt. Some within Labor claim the revelations and reporting of the speech cost Labor precious votes.

GEOFF GALLOP: I think the Labor Party is damaged goods. I mean, if you look at what's been going on in New South Wales, if you look at many of the issues related to the relationship between business and politics, you look at the pre-selection processes in WA, you look at the controversy surrounding Joe Bullock in the past couple of weeks of the campaign. I mean, the Labor vote just collapsed.

SABRA LANE: Federal Labor leader Bill Shorten was scheduled to deliver a speech today on further modernising the party. It was postponed after Mr Shorten revealed his mother, Ann, died yesterday. Mr Shorten still intends delivering that speech and will take time off now to grieve with his family in private.

Dr Gallop says if Mr Shorten achieves true reform, electoral success will be his. But he says change must include the wider community in pre-selecting Labor candidates in all seats, that the party must dilute union influence within its power structures and at the party's national conference where it decides national policy and he warns if the ALP remains wedded to the ideas and candidates of the past, it does so at its own peril.

GEOFF GALLOP: On the question of same-sex marriage, there's absolutely no reason why that should be a conscience vote. The only reason it is, is because there's a strong faction within the party that wants to keep it that way. So Labor's capacity to present itself with what is a popular issue is totally constrained.

SABRA LANE: If the Liberals win three seats, it'll end up with 33 senators in total and will need another six votes to pass legislation, assuming the Greens and Labor block it. Given the commitment by Motoring Enthusiast's Ricky Muir to vote with the Palmer United team, it means Clive Palmer's bloc of four senators will share the balance of power with another four senators. And while most of the crossbench, including the Liberal Democrat David Leyonhjelm, are conservative leaning, he says nothing should be assumed on how they'll vote. And he doubts the Palmer team will vote as one.

DAVID LEYONHJELM: It's difficult to imagine them all lining up and saying, "I agree with Clive Palmer on this issue," and voting accordingly for the next three years, six years, whatever. I don't think that's likely to happen. And particularly when you look at the individuals involved. Jacqui Lambie in Tasmania is her own woman. She's not anybody's puppet.

SABRA LANE: The Prime Minister says the new senators should acknowledge his mandate to repeal the carbon and mining taxes.

DAVID LEYONHELM: We respect the Government's mandate up to a point, but we have our own principles and policies as well. So, we didn't get elected to implement the Government's policies, we got elected to pursue our own policies. But having said that, we'd certainly vote in favour of repeal of the carbon tax and the mining tax. There's no question about that.

SARAH FERGUSON: Sabra Lane reporting.