The Senate, bordering on the farcical all year, has finally descended into burlesque, with the tale of the bright young cabinet minister whose mum made him a son of her parents’ old country.

Before the strange case of the Nationals’ Matthew Canavan burst into public view, the Senate had already lost four of its number, under various parts of the Constitution’s Section 44, including the Greens’ two co-deputies within a week.

And then there’s been the media chase after One Nation’s Malcolm Roberts, in pursuit of documents to back his assertion he didn’t hold British citizenship when he nominated for the Senate.

Canavan’s story of how he was signed up for Italian citizenship – unknown to him, he says – by his Australian-born mother of Italian heritage, is as bizarre as they come.

It’s anyone’s guess whether the High Court will find he’s in breach of Section 44, which rules out dual citizens standing for parliament.

There are differences here with the circumstances of the two Greens, who were born overseas and hadn’t quashed their other citizenship, making their ineligibility clearer cut. Neither chose to dispute the situation.

Legal experts are unsure what the High Court may conclude on Canavan. There are also claims and counter-claims of what one is required, or not required, to do to become Italian.

So, it is not surprising the government has decided to fight for Canavan, who has resigned as a minister while his parliamentary status is determined.

For the Nationals, the stakes are particularly high and complicated.

If Canavan were found ineligible to have been elected, there’d be a countback, with his replacement being Joanna Lindgren, a former senator who lost in 2016. Lindgren is a grand-niece of the late Neville Bonner, the first Indigenous person elected to federal parliament.

A Liberal when she was a senator, Lindgren would likely find herself in the Nationals’ partyroom.

Where she sat would not be her decision but that of the Queensland Liberal National Party. The two parties are merged in that state, though they’re sharp-elbowed bedfellows, who break into their separate tribes once in Canberra. It is understood the LNP would not allow the loss of Canavan to disrupt the present balance of numbers coming out of Queensland.

Until the court case is decided – by year’s end on the optimistic assessment – Nationals leader Barnaby Joyce is acting in Canavan’s resources and northern Australia portfolio.

This will overload Joyce, who already looks under strain, this week making injudicious comments about the alleged theft of water by irrigators. Even if Canavan survives, his immediate absence from cabinet is a blow to Joyce, because he provides policy heft.

If the case goes against Canavan, Joyce would face a dilemma in who to elevate to cabinet.

The most obvious choice, on seniority and experience, would be the only National in the outer ministry: Small Business Minister Michael McCormack. But McCormack is from New South Wales. The Nationals would be desperate to keep up their representation from Queensland, a vital state for them, and the Coalition generally, at the election.

Queenslander Keith Pitt is an assistant minister, but his critics say he’s been difficult rather than supportive in that role. Then you get to backbenchers such as senator Barry O'Sullivan, based in Toowoomba, and David Littleproud, from the regional seat of Maranoa.

Littleproud is spoken of as a man with a future, but is a newcomer. There are wildly opposite views on O'Sullivan, a one-time detective and later businessman, whose performances with Senate committee witnesses can resemble the tougher side of police interrogation. His critics think he should be bumped from the Senate ticket at the next opportunity; his admirers believe he could be cabinet material.

The High Court decision on Canavan will at least provide clarity on a more obscure aspect of the dual citizenship ban.

Inevitably, however, the slew of actual or potential victims of Section 44 has led to calls for constitutional change.

There are arguments for and against the dual citizenship prohibition but convenience should not be included. Notwithstanding the peculiar Canavan situation, surely aspiring politicians should be able to ascertain if they have a foreign citizenship.

On the question of substance, some argue that in a multicultural community there should not be a requirement to relinquish citizenship of another country. There is the counter argument – which I think is more compelling – that the single allegiance is a reasonable condition to impose on those responsible for making national decisions.

Dual citizenship could throw up perceived conflicts of interest – for example, for trade or foreign ministers.

Two other parts of the wide-ranging Section 44 claiming victims this year relate to having a direct or indirect pecuniary interest in an agreement with the Commonwealth, designed to prevent corruption and conflicts of interest, and being “under sentence, or subject to be sentenced” for an offence carrying a year or more imprisonment.

The eligibility of a House of Representatives Nationals MP, David Gillespie, an assistant minister, is being challenged in the High Court by Labor on the ground of having an indirect pecuniary interest, because of a post office located within a shopping centre owned by a company in which he is a shareholder.

In 1977 Malcolm Fraser won a change to Section 15 of the Constitution to ensure a casual Senate vacancy is filled by a member of the same party. This followed shenanigans by a couple of conservative state governments in filling vacancies in the Whitlam government’s time.

That change was simple and demonstrably the right thing to do. In contrast, an attempt to alter the dual citizenship ban – and indeed any other qualification rule in Section 44 – would be more contested. That, and today’s generally negative electoral mood, would likely doom any referendum.