As it seeks to focus the campaign agenda on the bread-and-butter issues that might actually deliver it victory, the last thing Labor needs is for attention to be diverted by preselection turf wars and the factional and union power struggles that underpin them.

However, that’s exactly the position the party finds itself in following two developments yesterday, one accidental and the other self-inflicted.

The misfortune relates to the looming disendorsement of its candidate for Fremantle, one of three seats left to Labor in Western Australia after successive disasters in 2010 and 2013.

Chris Brown had emerged the victor of a keenly fought preselection process held after the incumbent, Melissa Parke, surprised all comers by announcing her retirement at the end of January.

In what might have been viewed as a proxy war for the party’s heart and soul, Brown was opposed by Josh Wilson, a staffer to Parke and the deputy mayor of Fremantle.

While Wilson impressed as a safe pair of hands, his endorsement may have invited grumbling that yet another prized seat had gone to a political professional with no immediately obvious connection to the working class.

Brown was a different kettle of fish entirely, having spent most of his working life as a wharfie — a fact of potent symbolism in the portside electorate, even if the industry’s days as a large-scale employer have long passed.

More to the point, Brown had recently taken up a position with the Maritime Union of Australia, which has been on a mission in recent years to establish a power base in Labor’s state branch.

The union had considerable success in mobilising its members to join the party, and in so doing contributed to the growing muscle of the blue-collar Left unions at state conference.

However, the union had thus far been unable to translate that influence into seats in Parliament, and it ran the risk that its members would lose their enthusiasm for party affairs if it didn’t get some runs on the board.

In the event, the industrial unions proved successful in negotiating Brown into a winning position on the party’s state executive, which overwhelmed a 155-110 winning margin for Wilson among the local party membership after its votes were added to the preselection ballot.

All that has now unravelled with the revelation that Brown failed to disclose spent convictions on his nomination form dating from the tail end of his teenage years, 31 years ago — one for the garden-variety youthful indiscretion of driving under the influence, but the other on the more problematic charge of assaulting a police officer.

Brown protests that the contact arose accidentally while he was defending himself from an unprovoked attack by three assailants, and says the court recognised mitigating circumstances when it gave him a good behaviour bond.

Furthermore, he claims to have raised the matter with party officials in April, only to be told that spent convictions did not have to be disclosed (although the question on the nomination form is whether the prospective candidate has “ever been found guilty of any offence”).

Some of that may have warranted sympathy under more settled circumstances, but there was already a certain wariness within the party’s upper echelons over Brown’s background in a proverbially militant trade union.

Labor has developed something of a habit in recent years of using disendorsements and expulsions to signal its distance from the rough end of the union movement during election campaigns — particularly during the time of Kevin Rudd, who by some accounts blocked Electrical Trades Union boss Kevin Harkins’ bid for a Tasmanian Senate seat because he had him confused with somebody else.

The party’s national executive is expected to resolve the issue by meeting today to replace Brown with Josh Wilson.

Much of the initial reaction has focused on the possibility that Fremantle could fall to the Greens — partly a legacy of a Greens byelection win in the state seat of Fremantle in 2009, but also because it chimed with other narratives that have dominated the first week of the campaign.

In reality, the Greens vote drops off sharply beyond the immediate orbit of Fremantle’s town centre, making them a lot less competitive in the larger federal electorate than they are in the smaller state one.

Labor had more reason to fear that Brown’s troubled past would drive swinging voters to the Liberals, who also stand to benefit from the loss of Melissa Parke’s personal vote and a relatively strong flow of Greens preferences now that their party is led by Malcolm Turnbull rather than Tony Abbott.

Obviously this does little to mollify the MUA, whose deep sense of outrage will disturb the tranquility of the state branch as it gears up for what had been looking like a fairly promising federal election, if only by its recent dismal standards.

The other big news on the Labor preselection front was the resolution of the Senate ticket by the South Australian state executive, and the shock revelation that second position had gone to Don Farrell, the former national president of the Shop Distributive and Allied Employees Association, and a standard bearer for the socially conservative tendency the union traditionally represents.

Farrell was elected to the Senate after a long career as a backroom operator in 2007, and further demonstrated his influence when the party’s state conference awarded him top position on the Senate ticket ahead of the 2013 election.

This involved relegating Penny Wong to No. 2, prompting a fierce backlash spearheaded by Labor all-rounder Anthony Albanese, who described the decision as “gross self-indulgent rubbish”.

Farrell graciously agreed to exchange places with Wong, but the issue was seen at the time as being largely symbolic, given the long-established certainty that both major parties could rely on at least two seats out of six in any given state at a normal half-Senate election.

However, this was up-ended when Labor’s Senate vote in South Australia crashed to 22.7% in the face of Nick Xenophon’s breakthrough, leaving Farrell high and dry.

When factional ally Michael O’Brien agreed to make his state seat of Napier available to Farrell at the state election in March 2014, Jay Weatherill scotched the plan by threatening to quit as Premier if it came to fruition.

Farrell’s unplanned exit from politics was followed more recently by the departure from the Senate of another SDA warlord, Joe Bullock, the former secretary of the union’s Western Australian branch.

When Bill Shorten filled the Bullock vacancy with his captain’s pick of Pat Dodson, a factionally unaligned indigenous leader (albeit that he is also a social conservative and a former Catholic priest), the SDA was surprisingly docile in its response.

The solution to that particular mystery can perhaps be found in Farrell’s seamless move into the unloseable second spot on a double dissolution Senate ticket, despite the 61-year-old’s meagre prospects for future promotion.

This time though, the victim of Farrell’s ascendancy is not Penny Wong, who maintains top position on the ticket.

Rather, that unfortunate distinction goes to Anne McEwen, one time secretary of the Left-aligned Australian Services Union, who has been bumped to a number four position that looks highly precarious in the face of another Nick Xenophon onslaught.

*To read more from Crikey‘s William Bowe, visit The Poll Bludger