Coalition MP Kevin Hogan has left the door open to sitting on the crossbench if Bill Shorten wins the May election, turning him into a key figure in the event of a hung Parliament.
Mr Hogan, who is under threat from Labor in the northern NSW seat of Page, said he would "review his position" if he was re-elected.
Pressed repeatedly on whether this meant he could support a Shorten Labor government through confidence and supply, Mr Hogan insisted he would review his position after the election.
He later added that this did not mean he would guarantee confidence. "I'm not guaranteeing them anything," he said.
The Nationals MP faces a battle to hold onto his seat if there is a swing against the government; he sits in one of three key seats in northern NSW, along with the Coalition strongholds of New England and Cowper.
Internal polling shows in a worst case scenario Mr Hogan is 52-48 ahead of Labor candidate Patrick Deegan.
Polls have tightened next door in Cowper, where Nationals operatives have all but given up hope of saving the seat from former high-profile independent Rob Oakeshott.
An increasingly confident Mr Oakeshott said voters were ready to make the Coalition pay over leadership instability and a lack of climate change action.
"There was a government elected on a platform of not ripping down prime ministers and promising an alternative to a carbon tax and they failed miserably on both," he said.
"There are frustrations on both those topics that in my view have the government pretty well cooked."
Mr Hogan has sat on the crossbench in the House of Representatives since August in protest at the leadership spill that toppled Malcolm Turnbull, but has remained in the Nationals party room.
Despite his personal unease with the circumstances that led to Mr Turnbull's downfall, he said voters had begun warming to Prime Minister Scott Morrison.
"While he was a high profile minister there were still a lot of people who did not know him," he said. "I get the feeling that he is growing on people."
Former deputy prime minister Barnaby Joyce said Mr Hogan's future was a matter for him.
"As a former leader of the National Party, I am quite obviously on the other side of the fence to the Labor Party," he said. "I am going to be unambiguous with where my views lie."
Mr Joyce is facing his own challenge in New England, where rising independent Adam Blakester is running a crowd-funded Cathy McGowan-style campaign.
Voters and business are increasingly frustrated by the drought and controversies surrounding Mr Joyce but he remains the favourite to win in May. On Saturday, the government will announce $90 million in concessional loans and small business support for drought-affected farmers.
In his first interview since an explosive and rambling exchange on ABC radio over an $80 million water-buy back deal, Mr Joyce defended his decision to speak out - arguing the story was being pushed by political interests and "vomited out" by journalists.
The government has asked the Auditor-General to investigate the 2017 deals with a company co-founded by Energy Minister Angus Taylor. Mr Taylor has said he has had no contact or relationship with the company since he became an MP in 2013.
"I was incredibly angry at the assertion that I used my piggy bank to pay money to my mates," Mr Joyce told The Sydney Morning Herald and The Age.
"That is a statement of corruption. It is absolutely, utterly, bull."
Mr Joyce said he had feedback that "he had been too vociferous in my defence" but had to "knock it on the head straight away".