A startling wake-up call at the NSW election and bubbling federal leadership tensions have cast a shadow over the junior coalition partner's build-up to the May poll.

Deputy Prime Minister Michael McCormack has been criticised for lacking the cut-through of Barnaby Joyce who continues to make his presence felt in the media.

McCormack was given the leadership as the safe option following Joyce's high-profile affair with a staffer-turned-partner.

But some nervous MPs are worried McCormack's tendency to fly under the radar might clip their wings as the spectre of angry regional voters looms large in marginal seats.

The election campaign could emerge as a de facto leadership contest as McCormack and Joyce hit the hustings in the bush.

Wild swings against the Nationals in western NSW saw the party cough up two heartland seats to the Shooters, Fishers and Farmers at the March state election.

In Queensland a rump of nervous Nationals have inflamed leadership ructions against McCormack, but it remains to be seen if a commitment to a feasibility study for a coal-fired power station will placate them.

Michelle Landry holds Capricornia with a wafer-thin 0.6 per cent margin, while Ken O'Dowd has a one per cent buffer in Flynn.

George Christensen - who has repeatedly made empty threats to cross the floor and quit the party - holds Dawson by 3.4 per cent.

Environment Minister Melissa Price's decision to approve the groundwater plan for Adani's controversial Carmichael mine will also be welcomed by Queenslanders including Resources Minister Matt Canavan.

NSW MP Kevin Hogan holds the northern rivers seat of Page with a margin of 2.3 per cent, while on that seat's southern border the Nationals are facing a challenge from former independent MP Rob Oakeshott.

With Hartsuyker retiring, rookie candidate Patrick Conaghan is the outsider to hold Cowper for the Nationals after Oakeshott shaved the margin to 4.5 per cent at the last election.

While sandbagging seats held before the election will be a priority, the Nationals also have a series of three-cornered fights where they'll be desperate to gain ground in NSW and Victoria.

The Nationals' historic low was reached at the 2007 election when Kevin Rudd swept Labor to power after 11 years of conservative rule and the country-based party was reduced to 10 lower house MPs.

But former leader Warren Truss, who reluctantly took the reins after that election, cautioned Nationals against despair if they cop a hiding at this year's poll.

"The pendulums do swing. The disappointment we all had in losing in 2007 was all forgotten after the success in 2013," he told AAP.

McCormack will survive until the election but if voters brandish baseball bats in the bush, his leadership could be terminal.

"Let's worry about the election after the election," he said in the day before the April 2 budget.

"We've provided great outcomes for regional Australia and we've done that with me as the National Party leader."

The Nationals are staring down the barrel of the party's lowest Senate representation in 15 years if their numbers are sliced from six to four.

Outspoken Queenslander Barry O'Sullivan was rolled in a pre-selection battle last year and will be replaced by moderate businesswoman Susan McDonald.

In NSW, John "Wacka" Williams will bow out of federal politics, but Perin Davey is unlikely to replace him after being placed behind two Liberals on the coalition's joint bid.

The coalition will have a a new Northern Territory senator after the election, with Katherine vet Samantha McMahon set to replace pig-hunting Indigenous Affairs Minister Nigel Scullion.

Tasmanian recruit Steve Martin's thylacine-style attempt to bring the party out of extinction on the island looks as though it will be short-lived.

The storm fronts are rolling in, but it's how the Nationals weather the election that will determine the party's future.

Australian Associated Press