David Layzell will contest the Upper Hunter byelection for the National Party

NSW Nationals leader John Barilaro with the candidate for Upper Hunter by-election David Layzell.
NSW Nationals leader John Barilaro with the candidate for Upper Hunter by-election David Layzell.

NSW Premier Gladys Berejiklian will head to the Upper Hunter next week to campaign alongside the newly chosen by-election candidate she says is an underdog.

Little-known Clarence Town construction manager David Layzell was anointed the Nationals' candidate in the crucial May 22 by-election in a vote on Wednesday evening.

"We are no doubt the underdogs," Ms Berejiklian said on Thursday, pointing to a history of large swings against governments in by-elections.

But she said she was looking forward to campaigning with Mr Layzell next week.

"We'll work our guts out to demonstrate to the people of the Upper Hunter why we deserve to have David elected as their local representative. It won't stop us fighting," she said.

Mr Layzell carries the hopes of the coalition government, as a loss in the regional Upper Hunter seat would leave the government in minority until the 2023 election.

Deputy Premier John Barilaro told the premier Mr Layzell's speech at the branch's preselection meeting was outstanding, she said.

Mr Layzell beat out the favoured contender, long-term Singleton mayor and cattle farmer Sue Moore, in a surprise victory.

Mr Barilaro and NSW Treasurer Dominic Perrottet were already on the campaign trail with Mr Layzell in the regional electorate on Thursday, giving a news conference at Glencore's Ravensworth mine in the Hunter Valley.

The government sees the uncertain future of the coal industry as a crucial battleground in the election, with the electorate being home to a significant population of miners.

Mr Perrottet wrote in the Daily Telegraph on Thursday that "the death of coal has been greatly exaggerated".

He said Labor's federal MP and coal spruiker Joel Fitzgibbon was a "pariah in his own party because of his support for coalmining".

"With the Liberals and Nationals you know what you are getting. We have always backed Hunter mining, and we will always prioritise the people of Parkville over virtue-signalling and pandering to elites in Paris," he wrote.

Mr Layzell said he looked forward to fighting the election on local issues.

"Central to that is strong mining and agriculture industries so people continue to have secure jobs," he said.

The by-election was sparked by Nationals MP Michael Johnsen's resignation on March 31 after he was accused of raping a woman in 2019, which he denies.

Mr Johnsen's conduct is likely to sway voters, as could the closure of the Scone TAFE.

Ms Berejiklian's government was elected with a two-seat majority in 2019, but Liberal MP John Sidoti has since moved to the cross bench amid an ICAC investigation.

The May 22 by-election race is expected to be tight despite the Nationals and its predecessor party holding the electorate for nearly a century.

The seat was whittled away to a margin of just 2.6 per cent at the 2019 election, when Mr Johnsen scooped up 34 per cent of first preferences.

Labor trailed on 28.6 per cent and the Shooters, Fishers and Farmers Party candidate on 22 per cent.

One Nation will also contest the by-election.

Labor has yet to preselect a candidate and the SFF Party expects to announce its candidate next week.

Australian Associated Press