A preference deal with the Shooters, Fishers and Farmers Party could deliver Labor the seat of Upper Hunter for the first time in the electorate's history.
Upper Hunter is shaping as a potential loss for the Coalition in Saturday's state election as Nationals incumbent Michael Johnsen clings to a 2.2 per cent majority.
Labor how-to-vote cards place the Shooters second in Upper Hunter.
The Shooters how-to-vote card does not include numbered preferences but says: "If you want change, you need to fill in the boxes and put the Nationals last."
Shooters candidate Lee Watts, a Scone councillor and former mayor, won 19.4 per cent of the primary vote when she ran in Upper Hunter as an independent in 2015.
Muswellbrook mayor Martin Rush gained a swing of 20.8 per cent against Mr Johnsen that year, winning 32.5 per cent of the primary vote, but withdrew from this year's race over anonymous allegations of an altercation with a female flatmate.
Melanie Dagg has taken up the reins for Labor, who think they have a good chance of taking a seat which has voted for the Nationals in 21 consecutive state elections.
Sportsbet's election market lists Ms Dagg as a clear $1.60 favourite on Saturday, ahead of Mr Johnsen at $2.10 and Ms Watts at $9.
Ms Dagg is Cessnock deputy mayor, but her popularity in the Upper Hunter electorate is untested.
A Shooters source gave Ms Watts an outside chance of springing an upset in a three-cornered contest if Labor preferences flow her way.
The Coalition holds a six-seat majority but faces close calls in a handful of seats across the state.
A YouGov-Galaxy poll released on Monday showed swings against Liberal MPs of five and six per cent in Penrith and Goulburn respectively.
But the Coalition has sought to make political mileage out of Labor's deal with the Shooters, especially in light of Friday's mosque shootings in Christchurch.
Former prime minister John Howard warned while campaigning with Premier Gladys Berejiklian in Penrith on Monday that the Shooters would seek softer gun laws if Labor won on Saturday.
Opposition leader Michael Daley has vowed to resign if gun laws are relaxed.
Asked about the preference deal on Monday, Ms Dagg said: "What has happened in New Zealand, we shouldn't be playing politics with that.
"But, in terms of a preference deal, that's all handled by head office, so it is what it is, I guess."
Maitland MP Jenny Aitchison echoed the view of Mr Daley when she said the preference deal was about securing a change of government.
"We are giving them [voters] an indication that the most important thing is putting the Nationals and Liberals last. That is the focus that we're doing," she said.
"We won't preference One Nation; we won't preference racist groups."