With more than a year to go before the November 2018 state election, the group traditionally in control of the Victorian party's right faction is facing open attacks in at least two seats.

The left's powerbrokers are also seeing their grip on power slip.

The two western Melbourne seats left vacant in the wake of the second residence allowances scandal, first revealed by The Age, are set to be at the centre of the upheaval.

Melton and Tarneit, to be vacated by disgraced Labor MPs Don Nardella and Telmo Languiller, are "in play" as the party's complex factional landscape faces major upheaval.

Mr Languiller announced last month that he would not be seeking preselection while Mr Nardella, who was kicked out of the party and now sits as an independent, has said he will not contest the election.

The seats are tightly-held real estate, with Mr Nardella elected to Melton in 1999 while Mr Languiller was elected in the now-abolished Sunshine electorate in the same year.

The starting salary for backbenchers is about $148,000.

The Western Metropolitan Upper House seat held by Khalil Eideh, currently embroiled in allegations of rorting Parliamentary printing allowances, is also likely to be up for grabs, with the embattled MP considering retirement.

Nominations for preselection do not open until September 22, but already members of a Labor right "sub-faction" controlled by former state minister Adem Somyurek are challenging footsoldiers of the group loyal to long-time Labor warlord and former federal minister Stephen Conroy.

Mr Conroy's forces are understood to be confident they can hold onto Tarneit and Footscray while acknowledging they face some challenges.

Labor veteran and former minister Marsha Thomson is likely to face a challenge for her safe Footscray seat from a party figure associated with Mr Somyurek's grouping.

This - challenging a sitting member in what is a first-term government - would be a particularly aggressive move.

Mr Conroy left the Senate in 2016 but remains a key player in the Victorian right faction, despite internal party rumblings that his day-job as a gambling industry lobbyist makes him unsuitable to wield such power.

Party sources say the discontent is being harnessed by Mr Somyurek as he and his allies launch an insurgency against the status quo in the right faction.

Labor figures say there is a "changing of the guard" underway as the power of Mr Conroy and long-time left faction strong man Senator Kim Carr wanes.

An informal peace agreement between the two men has long been a key pillar of Labor Leader Bill Shorten's Victorian power base.

But one Labor source said the coming state preselections would reveal how far Senator Carr and Mr Conroy's influence had been eroded with the challenges in Footscray and Tarneit underscoring the move to marginalise Mr Conroy.

In Tarneit, a safe-as-houses Labor seat which it holds with a margin of nearly 15 per cent, Mr Somyurek is backing Sarah Connolly for preselection, while rival Jasvinder Sidhu, has Mr Conroy's support.

In Melton, the selection of a successor to Mr Nardella will be a test of Senator Carr's continued influence.

Former Melton mayor Justin Mammarella confirmed he would nominate for preselection in Mr Nardella's seat.

The allegations against Mr Eideh, a member of Senator Carr's group, do not help the former federal minister as he works to keep his power base together.

A party source told Fairfax Media on Tuesday that the Somyurek camp was trying to deprive Mr Conroy of supporters by challenging their pre-selections.

"Stripping [Mr Conroy] of MPs is a very powerful way of making sure his influence is diminished," the source said.