Just independent candidate Jim Doukas and Family First candidate Chris Brunt have preferenced Ms Britnell ahead of Labor candidate Kylie Gaston and independent Carol Altmann.

Independent candidate James Purcell, who registered 16.5 per cent of the vote in the 2018 state election, has preferenced independents Mr Doukas and Michael McCluskey, and Labor's Ms Gaston above Ms Altmann and Ms Britnell respectively.

Greens candidate Thomas Campbell has Ms Altmann placed second while Labor's Ms Gaston is preferenced above Liberal's Ms Britnell.

Meanwhile, the Liberals have still flagged Labor as their main rivals in South West Coast with Ms Britnell's how-to-vote card placing Ms Gaston last. Ms Altmann is placed sixth.

Labor's Ms Gaston has preferenced Mr Campbell second, and Mr Purcell and Ms Altmann ahead of Ms Britnell.

Deakin University politics lecturer Geoffrey Robinson said he thought the main challenger to sitting member Ms Britnell was Ms Altmann.

"It's a pretty favorable environment for Altmann," he said.

"I think it's a two-horse race (between Ms Altmann and Ms Britnell).

"If (Ms Altmann) could get ahead of Labor, (she'd) probably be in a pretty strong position."

Dr Robinson said there may be a likelihood the electorate's traditional Labor voters would use their vote strategically to oust their perennial opponent.

"It may depend on if voters strategically, thinking that they can't win, find support behind the independent," he said.

"I noticed Roy Reekie, the former Labor candidate saying nice things about Altmann.

"I imagined that he's been out there among lots of Labor voters... to vote for Altmann in the interests of defeating the Liberal."

He said Ms Altmann's path to victory would have to involve carving out portions of the Green vote - which helped independents in the federal election - and winning some support from Mr Purcell's base.

"Most of the support would be coming from Labor and the Greens, then she's going to need to attract some people who voted for Purcell last time," he said.

But Dr Robinson said independent James Purcell's preferences going to Labor ahead of Ms Altmann could hurt the latter's chances.

"That's maybe a potential problem for Altmann," he said.

"On the other hand, people who vote for independents often tend to think... 'I can give my vote to another independent as well'."

IN OTHER NEWS

Monash University politics lecturer Zareh Ghazarian said he would expect the Liberal Party to hold on to South West Coast given a likely statewide swing against the Labor government.

"Generally in traditional elections, more often than not, governments tend to lose support," he said.

"If that's the case then... the Liberal Party should hold."

Dr Ghazarian said preferences would be crucial for South West Coast given the slim margin from the 2018 state election - which is now 3.2 per cent after electoral boundary redistributions.

"If it's as close as it was last time... preferences will be very important," he said.

"Based on the field of candidates, and the preferences, this is definitely a seat to watch."

He said he also expected a swing away from major parties given the trend in the federal election.

"As we saw... Victorians were happy to vote for non-major party candidates," he said.

Dr Ghazarian said it was a "double-edged sword" for independents not to preference but did not think Ms Altmann had hurt her chances by not making any deals with other candidates.

"In Carol's case, she's trying to demonstrate that she has no affiliations or sympathy for any major party and is contesting as the independent," he said.

"But on the other hand, if it is a tight contest, preferences can determine who wins."

He stressed preferences operated on assumptions, and voters might number their ballots differently, but he said up to 60 per cent of Victorians had followed how-to-vote cards in past elections. "It's still an important tool," he said.

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