One of the benefits of having Warren Truss as loyal deputy has been his calm, assured, no-fuss manner.

Joyce’s approach to politics is the polar opposite.

As Labor frontbencher Penny Wong says: “Barnaby is very entertaining, but he is erratic and that’s the last thing you want in someone who is one step away from being the prime minister and who is called upon to act as prime minister.”

Joyce was dumped from the Coalition’s crucial finance portfolio in 2010 after a series of headline-making gaffes.

Since becoming a cabinet minister in 2013 he’s been at odds with colleagues over a range of issues.

For some it’s just a case of Barnaby the champion of the Nationals’ rural constituency speaking his mind.

For others he’s an old-school protectionist who wants to shelter Australia – especially agriculture – from the rest of the world.

One of the sleeper issues of the next election will be the fight between agriculture and mining.

Joyce’s NSW seat of New England is at the heart of the battle, as Shenhua Watermark seeks to develop a coal mine near prime agricultural land.

And it may be about to get complicated, for Joyce and the government, if retired MP Tony Windsor throws his hat in the ring.

Windsor, a staunch opponent of the mine, was in Canberra this week and is believed to be close to a decision on his future.

In September last year, Joyce said in an interview the business case for large coal mines no longer stacked up.

This was due to the price of coal dropping and the rising cost of bringing mines online.

His position is at odds with key figures in the Nationals, including the party’s federal president and former mine lobbyist Larry Anthony, and cabinet colleagues.

When Environment Minister Greg Hunt last year said the Watermark mine could go ahead if it met strict conditions, Joyce’s response was “ridiculous”.

“I think the world has gone mad,” Joyce wrote on his Facebook page.

Hunt says no federal environment minister could have knocked back the proposal based on the scientific, legal and departmental advice he had received.

Other members of cabinet such as Energy Minister Josh Frydenberg believe there is a “strong moral case” for Australia to continue exporting coal because it burns cleaner than that mined elsewhere.

Joyce has also been an opponent of higher levels of foreign investment – something key government figures say has been and always will be crucial to Australia’s economy.

And he’s been at odds with his Liberal coalition colleagues on deregulation of agricultural bulk exports and reform of competition laws.

Elevating Joyce to a more responsible position in cabinet puts him in an even more invidious position – torn between his ministerial responsibilities and his constituency.

The coming months may require him to focus more on his electorate, and the Nationals agenda, than his frontbench duties.

A poll taken in New England in August 2015 put him on 44.8 per cent of the primary vote, compared with 37.8 per cent for Windsor – translating to a narrow win by around one per cent to Joyce.

It’s a long drop from the 30 per cent margin with which Joyce took the seat in 2013, albeit without Windsor in the running.

Coal is not only a big issue in regional NSW.

A poll taken in October last year in the prime minister’s ritzy Sydney seat of Wentworth found six of 10 voters support a moratorium on new or expanded coal mines.

But Turnbull insists, like Frydenberg, that it’s better for Australia to keep developing and exporting coal because of its higher quality.

When Turnbull seized the leadership from Tony Abbott in September last year, Joyce – who has crossed the floor on critical votes in the past – made it clear the Nationals would continue to put their stamp on the Coalition.

“Don’t ever, ever doubt what my belief structure is and what I’m prepared to do,” he said.

“It’s not about personalities. It’s about values. It’s about what we want to deliver to regional people.”

Managing this tension will be crucial to the next phase of the Turnbull government.

AAP