Embattled Victorian opposition leader John Pesutto has denied a byelection in a Liberal stronghold in Melbourne’s northeast is a test of his leadership.

Factional warring among the Liberals has seen Mr Pesutto booed and jeered amid walkouts at the party’s recent state conference, with many rank-and-file members backing parliamentary-party exile Moira Deeming.

Ms Deeming is sueing Mr Pesutto, who sought her expulsion in the mistaken belief that was an associate of neo-nazis.

Labor, too, has its problems, choosing not to stand a candidate amid what polls suggest has been a backlash against Premier Daniel Andrews over the Commonwealth Games cancellation.

About 19,000 people are casting their votes on Saturday in the Warrandyte ballot, triggered by the retirement of veteran Liberal MP Ryan Smith.

Mr Smith released a resignation press release in July without informing Mr Pesutto, amid simmering factional tensions over the Deeming expulsion just months into her first term.

Candidate Nicole Werner is a virtual certainty to retain the seat for the Liberals over a field of mostly independents after Labor opted not to contest the byelection, although the final margin will be closely scrutinised.

Warrandyte is held by the Liberals on a two party-preferred margin of 4.3 per cent and hasn’t fallen out of the party’s grasp since 1988.

‘No seat is safe’

But Mr Pesutto said he wouldn’t pre-empt the by-election result.

“No seat is safe in politics these days,” he told reporters on Saturday, seemingly in reference Labor’s federal byelection win in Aston.

“You have to fight for every single vote … and at no stage in this Warrandyte by-election have we taken any votes for granted.”

Mr Pesutto said he was confident Ms Werner had mounted a strong case for voters. The charity manager and former youth pastor secured preselection after failing to reclaim the nearby seat of Box Hill for the Liberals last November, when Labor was returned for another four years in government.

“Nicole will be that strong voice,” Mr Pesutto said. “She’s grown up in the area, she’s a local and she wants to be a strong advocate for the people she wants to serve.”

A Victorian state byelection has not been held since 2017, when now-federal senator Lidia Thorpe snatched the seat of Northcote from Labor following the death of Fiona Richardson.

-with AAP