The Nationals' David Layzell has taken an early lead as the results start to trickle in from the Upper Hunter by-election in NSW.
The polls closed at 6pm on Saturday and about 3300 votes have been counted so far.
Mr Layzell has about 33 per cent of first preference votes, with Independent Kristy O'Connell on about 14 per cent.
Both major parties are sweating on the results, which could push the Berejiklian government into minority, or increase the pressure on Jodi McKay's position as opposition leader.
But it could be a long wait - there are 13 candidates on the ballot, and counting could take some days.
Preference flows are tipped to decide the contest with neither major party likely to win the seat outright.
The Nationals had held the seat by 2.6 per cent, before MP Michael Johnsen's resignation over sexual assault allegations and a sexting scandal prompted the by-election.
Mr Johnsen denies the allegations and has not been charged.
The by-election contest has centred on the future of coal mining in the region, with Labor and the Nationals talking up their coal credentials, and Labor candidate Jeff Drayton a former coal miner.
Labor has come close to winning the seat before, and hopes to rely on a history of by-election swings against governments.
Other candidates including the Greens' Sue Abbott and Ms O'Connell want to move the region away from its reliance on coal.
Candidates and their party leaders spent Saturday campaigning outside polling stations, but more than 40 per cent of the electorate had already made their minds up before Saturday, with some 23,000 votes cast early.
