After nominations closed for Labor pre-selections on Thursday, Mr Somyurek had taken another step in his quest for dominance of the party's right faction, and seems well on his way to controlling a powerful voting bloc.

Despite several weeks of feints, bluffs and threats in Labor and union circles, no attacks on sitting members had materialised by Thursday's 5pm cut-off for candidates to submit their paperwork to the party.

The coveted seat of Williamstown, left vacant by the surprise resignation of Employment Minister Wade Noonan on Wednesday, also emerged as a battleground with four potential candidates throwing their hats into the ring.

Multiple Labor sources said on Thursday that Mr Somyurek's forces now looked powerful enough to overcome opposition from their rivals in the party's right and take control of up to three safe seats.

His power in the Labor caucus is bolstered by an informal alliance with a small group loyal to former minister Jane Garrett, who will contest pre-selection for a safe upper house spot in Western Metro after walking away from her marginal Brunswick electorate.

Mr Somyurek's long-term goal of a return to the ministry remains unlikely during this term of government, but a frontbench comeback looks within reach after next year's election, regardless of the outcome.

It would be a dramatic reversal of fortune for the upper house MP who was humiliatingly sacked from his job as small business minister in 2015, after a complaint from his chief-of-staff, Dimity Paul, about threatening and intimidating behaviour.

Mr Somyurek maintained his innocence, alleging he was the victim of a factional vendetta and in an extraordinary press conference lashed out at his cabinet colleague James Merlino and others.

Since then he has been building alliances and striking deals - an effort about to pay off with a historic changing of the guard underway in Labor's factional landscape.

One Labor source told Fairfax that "Adem had been offered all sorts of inducements" to cease his "organisational activities" but he had refused.

Somyurek-backed candidates will contest pre-selections, against members of the traditionally dominant sub-faction loyal to former federal minister Stephen Conroy, in three safe seats that traditionally belong to the party's right and will not be contested next November by their sitting members.

Labor insiders says the Somyurek group is either sure to get the numbers they need or at least look very competitive .

In Footscray, the seat vacated by the retirement of Labor veteran Marsha Thompson, pre-selection looks likely for Somyurek loyalist Katie Hall over challenger Michael Clarke.

Vying to replace former speaker Telmo Languiller in the safe western suburbs seat of Tarneit are local hope Jasvindher Sidhu and Mr Somyurek's preferred candidate, Sarah Connolly.

The factional make-up of the Williamstown battle remains fluid, with the Somyurek camp having not yet chosen its preferred candidate on Thursday evening.

Another member of Mr Somyurek's group, Clare Burns, has already clinched pre-selection and is campaigning in the byelection in Northcote, the seat left vacant by the death in September of Minister for Women Fiona Richardson

Elsewhere, figures from the left of the party will square off against each other in the seats of Melbourne, Melton and Wendouree.

In Melbourne, former member Jennifer Kanis will battle ex-Army officer Dan Cairnes for the right to take on the Greens' Ellen Sandell next November.

In Melton, former Mayor Justin Mammarella looks strong against his opponent Michael Clarke, while in Wendouree Tom McIntosh from the industrial left will fight it out with Juliana Addison, who belongs to the group around long-term left factional player Adam Giles.

In Metro West, Ms Garrett's pre-selection must overcome the opposition of Australian Services Union secretary Ingrid Stitt, in what observers believe will be a tight race while a third hopeful Khaled Chakli, joined the race on Thursday.