A state by-election has shone a spotlight on a “forgotten” community and could further frank the nationwide shift to One Nation.

Thousands of voters will cast their ballots on Saturday for the Nepean byelection, triggered by the abrupt resignation of former tennis ace and Victorian Liberal deputy leader Sam Groth.

Oddsmakers have installed Liberal candidate Anthony Marsh as favourite to beat out One Nation’s Darren Hercus and main community independent Tracee Hutchison.

Since its inception in 2002, the Mornington Peninsula seat has been in Liberal hands for all but four years.

The electorate takes in the wealthy postcodes of Sorrento, Portsea and Flinders, but also low socio-economic areas such as Capel Sound, formerly known as Rosebud West.

Its general affluence means disadvantage in the middle of the electorate “disappears” for government decision-makers, Southern Peninsula Community Support chief executive Jeremy Maxwell said.

“We’re the forgotten part of Victoria down here,” he told AAP.

The Mornington Peninsula is officially part of metropolitan Melbourne, but does not have comparable services.

Public transport is limited or non-existent, with many locals travelling by car to Frankston for work and medical appointments.

The Liberals have promised $340 million to “completely rebuild” Rosebud Hospital, while One Nation has proposed redevelopment through a public-private partnership.

Mr Maxwell’s charity supports about 2100 locals and their families – almost one in five are homeless, with half sleeping rough.

An influx of young people flocked to the area during the pandemic, buying into lower-value areas and pushing up house and rental prices for disadvantaged locals.

“If you become homeless down here, you are three times more likely to be a rough sleeper than you are in the rest of Melbourne,” Mr Maxwell said.

The Rosebud charity does not receive any state government support.

The Liberals have made a $250,000 commitment if the coalition comes to government in November, with One Nation, community independent, Greens and Libertarian candidates also expressing support.

“We’ve just got to get the ALP to go ‘it’s easier for us to do something down here than to listen to the continual whinging’,” Mr Maxwell said.

Benjamin Moffitt, a senior politics lecturer at Monash University, predicts the Liberals will hang on to Nepean following a strong challenge from One Nation.

“The seat itself should not be very contestable traditionally for One Nation, in terms of the demographics, proximity to the city, education levels and even the relatively low ‘no’ vote for the (voice) referendum,” he said.

Labor has opted not to stand a candidate, despite holding Nepean as recently three and a half years ago, limiting its usefulness as a crystal ball.

But a strong One Nation showing would back up national polling and the South Australia election result, and bode poorly for the Liberals in the May 9 Farrer byelection and November Victorian election, the populism expert said.

“If they even do somewhat well in Nepean, that’s a real problem for the Liberal Party,” Dr Moffitt said.

“Farrer is about as good a situation as you could set up for One Nation. They could win and if they do … we’ll be reading the tea leaves for November.”

Tens of thousands of voters have been summoned to cast their ballots for a state byelection on Saturday, with three main contenders emerging.

Nepean byelection snapshot:

* 50,910 enrolled electors for Victorian state seat on the Mornington Peninsula, south of Melbourne

* Takes in the suburbs of Portsea, Sorrento, Blairgowrie, Rye, Cape Schanck, Flinders, Rosebud and Dromana

* Seat was created in 2002, replacing Dromana

* Held by Liberals until a shock win by Labor’s Chris Brayne in 2018

* Returned to Liberal hands in 2022 after Sam Groth won 48 per cent of the primary vote

* Mr Groth resigned in February, triggering byelection less than seven months out from the state election

Sam Groth resigned from the seat in February, triggering the byelection. (Joel Carrett/AAP PHOTOS)

Main candidates:

* Anthony Marsh – Liberal

– In his third term as Mornington Peninsula Shire mayor after being elected to council as an independent in 2020

– Former commissioned officer in the Royal Australian Air Force and founder of a drone safety app

– Previously declared he had “no political affiliations” and would “never” be a member of a political party

– In his own words: “I can no longer sit by and watch this bad Labor government destroy the region, and the state I call home. I’m ready to be part of a team that will make the tough decisions and the right decisions to change the direction of our state and the Peninsula.”

* Darren Hercus – One Nation

– Lives in Safety Beach with his wife and two adult children

– Qualified civil engineer with over 30 years of experience within the building and construction industry

– Owner of a joist and truss manufacturing business in Dromana

– In his own words: “Both major parties, Liberal and Labor, haven’t looked after this electorate at all. We’ve got a lot of issues with the cost of living, housing affordability, crime rates have increased. It’s just endless.”

* Tracee Hutchison – independent

– Grew up in Rosebud and McCrae

– A 30-year media veteran with roles at ABC youth radio station triple j, the 7.30 Report, Channel 7, Channel 9 and a community radio station

– Chair of Green Music Australia, the national peak body for the environment in the music industry

* Campaign backed by Independents for Mornington Peninsula

– In her own words: “The hospital where I was born needs to be rebuilt. Our roads need fixing. Our schools need investment … I’ve spent my career listening to people and giving voice to what matters most. Now I want to do that for Nepean.”

Sources: VEC, Liberal Victoria, Committee for Frankston & Mornington Peninsula, One Nation and traceehutchison4nepean.com.au and traceehutchison.com

—AAP