Data obtained by The Standard has shown the Melbourne Cup-style field will result in a volatile result on by-election night without former premier Denis Napthine's long-standing popular following.

The polling of 300 voters indicates that on primary votes, Liberal Party candidate Roma Britnell will gain 37 per cent, independent Roy Reekie, 24 per cent and National Party candidate Michael Neoh 18 per cent.

Other candidates make up the 21 per cent balance of the primary vote with Country Party candidate Jim Doukas popular with rural voters and independent Liberal Pete Smith performing well in the Portland region.

The polling indicates preferences will play a crucial role in the result, given no candidate is expected to reach the reasonably safe benchmark of 40 per cent of the primary vote.

Deakin University political expert Geoff Robinson said by-election polling was not always as accurate as national or statewide surveys. 

He said the Liberal Party was likely to retain the seat with a reduced majority.

“Napthine had a strong following and his time as premier meant he was not hit with a pro-Labor swing in his electorate that occurred elsewhere across the state,” Dr Robinson said.

“Local recognition will play a key role. By-elections sometimes produce unusual results because the voter is focused more on candidates than statewide issues.”