If losing one MP may be regarded as a misfortune, and a second looks like carelessness, it’s hard imagine what word might apply to the Western Australian branch of the ALP right now.

In the opening months of the year, fully four out Labor’s six federal parliamentarians have announced their retirement, with all three House of Representatives to bow out at the election and Senator Joe Bullock to go in a matter of weeks, following his resignation announcement last week in protest over the party’s support for same-sex marriage.

One small upside for Labor is that a slew of new job opportunities have opened for aspiring MPs, who have had rather a hard time of it in Western Australia over the last few federal and state electoral cycles.

In finding the right pegs for the appropriate holes, the party must take into account the fine balance of competing power bases in the state branch, along with the electoral imperative to accommodate fresh talent from outside the suffocating union-factional complex.

It was with the latter objective in mind that Bill Shorten moved promptly to have Bullock’s vacancy filled by high-profile indigenous leader Pat Dodson.

That news was for the most part warmly received, even to the extent of being welcomed by the government’s Indigenous Affairs Minister, Nigel Scullion.

Inevitably though, Shorten’s “captain’s pick” has complicated knock-on effects for the outstanding preselection contests.

Bullock’s seat has long been a prize of the Shop Distributive and Allied Employees Union, having previously been held by another former state secretary of the union, Mark Bishop.

That the seat should now go to an unaligned outsider is particularly troubling for the SDA, as it was similarly deprived in South Australia after Don Farrell agreed to relinquish his spot at the top of the ticket to Penny Wong.

On the other side of the fence, Dodson’s anointment has again scotched the hopes of former senator and Left faction member Louise Pratt, who initially declared her interest in the position immediately after Bullock’s announcement.

To many on the Left, the vacancy at first looked like an opportunity to right the perceived wrong of the last election, when Bullock took top position on the Senate ticket at Pratt’s expense after a deal between the Right and the biggest Left union, United Voice.

As it did for Don Farrell in South Australia, the demotion proved fatal for Pratt, as Labor’s vote collapsed to the point where it was only able to win one out of six seats up for election.

Many attributed the Western Australian debacle to derogatory comments Bullock made about Pratt at an event held by a Christian group, news of which broke the day before the state’s Senate re-run election was held in April 2014 — for which Pratt, rather than Bullock, ended up paying the price.

Despite considerable sympathy among the party rank-and-file, Pratt has since struggled to find a pathway back to her old job.

Should the next election be a normal one for the House and half the Senate, Pratt will occupy the unwinnable third position on the party ticket behind incumbents Sue Lines and Glenn Sterle, who respectively emerged through United Voice and the Right-aligned Transport Workers Union.

Things could change though if there is a double dissolution, which could potentially net Labor a fourth seat.

While the best real estate on the Senate ticket would continue to be reserved for the incumbents, the No. 4 position would clearly be of interest to both Pratt and the SDA, who now have a grievance at being locked out of the Senate in common, if little else.

However, the complex balance of forces within the Left could potentially cruel Pratt’s hopes even if she overcomes the SDA, just as it did when United Voice’s deal with the Right sealed her doom in 2014.

Pratt’s base in the Australian Manufacturing Workers’ Union has traditionally been one of the two main centres of power in the faction, together with United Voice.

However, the AMWU has ceased to be the dominant force among the industrial unions in recent years, owing to the ongoing decline of manufacturing and the growing assertiveness of other blue-collar unions — most notably the Maritime Union of Australia, which has had considerable success in encouraging its members to sign on to the party.

After being frustrated in previous efforts to translate organisational muscle into seats in Parliament, the MUA is throwing everything it has at the preselection to replace Melissa Parke in the portside electorate of Fremantle — a fine symbolic prize for the union representing waterfront workers.

First, though, its candidate, union organiser and former wharfie Chris Brown, must overcome rival Left aspirant Josh Wilson.

Despite Wilson’s strong credentials as chief-of-staff to Parke and deputy mayor of Fremantle, indications are that the inside running is with Brown.

However, observers say that might change if the SDA, which currently plans to abstain from the preselection vote, can be persuaded to throw its weight behind Wilson. There are also suggestions that a win for Brown could fall foul of the party’s national executive, over concerns he would be unable to defend the seat from the Greens.

Should the MUA once again be thwarted in Fremantle, its eyes could very well turn to the fourth Senate spot.

Things are at least looking more settled in Labor’s other two lower house vacancies, with barrister Tim Hammond now confirmed as the candidate to succeed Alannah MacTiernan in Perth, and Gary Gray’s seat of Brand set to go to Madeleine King, chief operating officer of the international policy think tank Perth USAsia Centre.

As Labor would be keen to point out, only in Fremantle is there the prospect of a vacancy going to a union official, however much the union movement’s fingerprints may be found over the process as a whole.