In a year that has thrown up alignments and realignments, the most major realignment within Labor since the factional system began might have been saved until last.
It's been revealed that the former Victorian Right-dominating National Union of Workers (NUW) has been in talks to merge with current Socialist Left giants the Australian Manufacturing Workers' Union (AMWU) and United Voice (UV).
The trade union movement in general has been under pressure from the Coalition government, especially around costs related to the trade union royal commission.
The foundation union for the Queensland Right, the Australian Workers' Union, is said to be under extreme financial pressure, with debts in the millions and a dwindling membership base. The CFMEU and MUA are close to completing their merger, and United Voice in Queensland has launched a new branch named Hospitality United to boost membership.
NUW has most likely been driven to these unlikely merger talks by financial imperative. 
It would appear that Opposition Leader Bill Shorten's base, the Victorian branch of the AWU, is also in a weak financial position and unable to help their fellow Victorian Right union, after years of negative attention from the media and the trade union royal commission.
Left unions have mostly avoided the bad publicity and weren't called before the royal commission. 
The right-wing Victorian Centre Unity had only just coalesced into a workable bloc within Victorian Labor when NUW rejoined the fray with the AWU/TWU ShortCons (that is, supporters of Bill Shorten and the recently departed Stephen Conroy).
All power within the Labor Party rests with delegates on conference floors, and an alignment of NUW, AMWU and UV to form a "super union" the size of the SDA (the conservative "Shoppies") will have national conference and Victorian and Queensland state conference ramifications. [What will Conroy's departure mean for Shorten's leadership?]
Currently the Stability Pact partners of Socialist Left and Centre Unity both have 42% of Victorian Labor's conference floor.
In any NUW merger with AMWU and UV the NUW would be compelled by force of internal numbers to lend their membership towards an increased Socialist Left contingent on state conference floor. [All over the Shoppies]
This realignment would result in Socialist Left holding 50% of Victorian conference floor, with the Victorian Right unable to compete.
Let's not forget Bill Landeryou's NUW was the founding union of the Victorian Right, so this is a major shift. Bill's son Andrew, of Vexnews fame, is a confidant and numbers man of Bill Shorten. [Victoria's new senator could be a ticking time bomb for Labor] NUW is also the power base of the small Labor Unity faction in Queensland, currently in alliance with the Queensland Left.
The merger would present major issues for them and most likely collapse their whole faction. HSU, an ally of Bill Shorten's, is re-affiliating with Labor after years of scandal and restructuring, but their reaffiliation doesn't look like being able to overpower the shifts to towards Left dominance in Victoria, Queensland and nationally. Chris Brown, HSU's national secretary, is from the Left and on the party national executive, so it's uncertain how exactly the numbers would play out nationally.
This is all before we have the mostly left-wing rank and file directly elect their delegates to the next national conference.
A nightmare for Bill and an awful Christmas present.