Nationals leadership spill: Barnaby Joyce believes public have forgiven him for affair with Vikki Campion

Personal scandal forced the member for New England and former deputy prime minister's resignation in 2018 after it was revealed Mr Joyce had an affair with staffer Vikki Campion.

The pair now have two sons, Thomas and Sebastian, and two years on Mr Joyce said he felt enough time had passed to return to leadership.

"I have apologised profusely for incidents in my life and I think everyone deserves forgiveness and understanding," he said.

"I don't believe the Australian spirit lies in retribution."

Five politicians are expected to fight for the position of deputy leader of The Nationals and the agriculture portfolio that was up until recently held by Ms McKenzie.

She resigned after a report found she breached ministerial standards when she failed to disclose membership to a gun club that received almost $36,000 from a funding program she oversaw.

Tamworth was caught up in the "sports rort" scandal, after a council application to the grant scheme was one of the most highly recommended in the country but missed out.

Among the challengers for the deputy role is Water Minister David Littleproud, Lyne MP David Gillespie, Victorian MP Darren Chester and Queensland MP Keith Pitt.

Parkes MP Mark Coulton wouldn't rule out a crack when approached by the Leader.

"The leadership of the National Party is a matter for the party room, and I'm not going to speculate before tomorrow's vote on who will be the next deputy leader," he said.

Mr Joyce said he'd be happy to take on the agriculture portfolio, given he held it previously in the Abbott and Turnbull governments from 2013 to 2017.

The move has strained his relationship with Nationals leader Michael McCormack, but Mr Joyce argued "everybody understands the system and how it works".

"I suppose at the start of the year before [politicians] go to work, and two years out from an election, if there's an issue that needs to be dealt with, now is the time to deal with it," he said.

"Maybe my flaw is that if you're asked a straight question and you give a straight answer, it gets you into trouble."

The top priority for Mr Joyce, if he made it back onto the frontbench, would be to deliver the highly controversial Bradfield Scheme.

The idea is to take excess floodwater from north Queensland and use it to combat drought in southern parts of the state.

The 1930s concept has been rubbished by governments over the years, who reject its economic, scientific and engineering viability.

The concept has been rebranded by the Liberal National Party, creatively named the New Bradfield Scheme, and it's hoped to win votes in the next state election.

Whether or not there's a spill, Mr Joyce said he would respect the decision of the party.

"Hopefully I can say, 'Well, I was never a coward; I stood to be counted, to win or lose', and that's how I operate," he said.

"I get a sense of frustration when people complain but don't want to do anything about it.

"I understand that for some people they have concerns or disregard for me, and I understand completely, but they can't argue that I haven't delivered."

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