As if the Liberals aren't having enough trouble with the transaction costs of regime change to discourage any party from the coup road, now the Nationals are displaying angst over their leadership.

There's unhappiness that Deputy Prime Minister Michael McCormack isn't cutting through publicly, or throwing around enough weight within the Government. Those who'd like a change back to Barnaby Joyce are stirring.

Mr Joyce, having put his personal crisis behind him, is obviously feeling his oats. Being envoy on drought might be a minor job, but it has lifted his profile, given him a platform, and no doubt stoked his perennial enthusiasm for being out on the campaign trail.

In Parliament this week, it was obvious Mr McCormack was reacting to the pressure he's under from the muttering and criticism.

The Nationals' desire for a special agricultural visa might be a niche issue, but Scott Morrison's pushback on it has been used against Mr McCormack.

Asked in question time on Tuesday for his response to a report that "a very well-known Nationals stakeholder has been ringing around for about three weeks in the face of ineffective representation on the ag visa", Mr McCormack launched into an extraordinary, and revealing, tirade about anonymous backgrounding.

Sorry, this video has expired Nationals leader insists he has support of the party

"I've always been prepared to put my name to everything I've ever spoken to a journalist on," he said. "I will never, ever background a journalist, and I think there is a cancer in Canberra at the moment, and it's people who background journalists. It's no good for politics. It's no good for Parliament." He went on and on.

On Wednesday, Labor needled him again, taking up a fierce attack earlier in the day by shock jock Ray Hadley who, following Mr McCormack's I-don't-background assertion, claimed his office had leaked during Joyce's "trying times".

In response, Mr McCormack told Parliament that he stood by everything he'd said on Tuesday, then veered off into how he'd stood by various constituencies.

Hadley, who had his sights aimed at Mr McCormack when the Dutton challenge was underway, on Wednesday described him as weak-kneed, having no policy and bending any way to accommodate the Liberals — "a very unworthy person to be in charge of the National Party".

An out-of-sorts party

The upheaval that led to Mr Joyce quitting strained the Nationals, but other things as well have contributed to a deeply divided, out-of-sorts party, including unfulfilled ambitions, preselection losses, and marginal seat fears.

Mr McCormack, who was elevated to the leadership from the junior ministry in extraordinary circumstances, lacks the authority to impose unity on his party, especially when the Government appears to be headed for defeat.

In 2016 the Nationals, knowing the Malcolm Turnbull messaging wasn't going to work for them, successfully differentiated themselves from the Liberals. The ability to do that was helped by Mr Joyce's distinctive style and his toughness within the Coalition.

The Nationals will again need to project a distinctive identity in the coming election, which will be a challenge for Mr McCormack.

Right now, Mr McCormack needs to be on the front foot but, as shown by this week's parliamentary performances, he looks and sounds like he's on the back one.

Former Nationals leader Barnaby Joyce and his successor Michael McCormack. ( ABC News: Matt Roberts )

Joyce toeing a fine line

Mr Joyce simply signals his availability. Appearing on Sky with Labor's agriculture spokesman Joel Fitzgibbon (who'd asked Mr McCormack the provocative parliamentary questions), Mr Joyce on Wednesday denied making any calls seeking votes.

There's a fine line between being out and about and canvassing. Just being visible is all that's needed at this stage of a bid. And Mr Joyce doesn't hide his ambitions for a return.

"If it came up, and it was offered to me, I would take it, but I am not touting for it, I am not collecting the numbers for it," he said.

The Sunday Telegraph's Annika Smethurst wrote last weekend that no one in the 22-member Nationals party room could "confidently rule out" Mr Joyce "calling for a spill of the leadership before Christmas".

Within the Nationals, opinion is divided about whether something could happen before the end of the year. Mr Joyce's critics rule it out, saying he has only a handful of loyalists. Others, however, are uncertain about how things will pan out. Seriously contemplating a change of leadership raises big questions for a party that traditionally sticks to its leaders.

Especially when such a change would be returning to someone who, together with his campaigning strengths, carries significant baggage. Mr McCormack might be looking bad but how would Mr Joyce perform second time around? Is the party up to what would be a ride on the wild side?

And change brings fallout, usually more than anticipated. As one National says: "Is Barnaby a better leader than McCormack? Yes. But what about the transactional costs?"

If the Liberals lose Saturday's Wentworth byelection, it will become clear just how high transaction costs can be. On the other hand, a Wentworth loss would send shock waves through the Government as a whole, which would probably make for more instability in the Nationals.

Michelle Grattan is a professorial fellow at the University of Canberra and chief political correspondent at The Conversation, where this article first appeared.