An "electoral earthquake" led by a minor party may mean a by-election for a once safe NSW Nationals seat will come down to preferences, the state opposition leader says.
The election result is still unclear with under 2000 votes separating the incumbent NSW Nationals and the Shooters, Fishers and Farmers (SFF) party in a close race which could be decided by preferences.
The figures on the NSW electoral commission website on Sunday afternoon show Nationals candidate Scott Barrett had won 30.26 per cent of primary votes but Philip Donato from the SFF party, which has never held a lower house seat in the state, is not far behind.
"I take my share of responsibility for an electoral earthquake affecting the government of the Nationals in Orange," NSW Labor leader Luke Foley said.
The Labor party comfortably won in two other by-elections on Saturday, with Sophie Cotsis retaining Canterbury and Paul Scully keeping Wollongong.
"The more people I met, the more doors I knocked on, the more communities I visited; it was clear that there was a clear cut resentment towards the National Party," SFF candidate Phil Donato told AAP.
But he stopped short of claiming a victory which is unlikely to be confirmed until Thursday.
Mr Donato trails with 23.67 per cent of the vote but may take the seat thanks to Labor preferences.
Orange has been a safe Nationals seat since the end of World War II and was held on a 21.7 per cent margin.
Council amalgamations and Premier Mike Baird's back down on a ban of greyhound racing in NSW were issues that led the backlash, Mr Donato said.
"The people of this electorate just felt disenchanted and have lost the loyalty they'd shown in the last seven generations towards the National Party," he said.
Deputy Premier and NSW Nationals leader Troy Grant said he intended to continue as leader despite the disastrous showing in the seat of Orange.
Nationals MP Andrew Fraser says he will move for a leadership spill at the first party room meeting on Tuesday.
Mr Grant says the final result of the by-election isn't known but the massive swing against the Nationals sends a strong message to the the state government.
"The message for Macquarie Street is clear: Government is there to support communities and otherwise, should just get out of people's lives," Mr Grant said.
