The political careers of two Senate minor party do-gooders, the Family First Party's Bob Day and One Nation Party's Rod Culleton, have seemingly turned to dust, not from good works but clouded judgments.

Their extramural activities have thrown the composition of the Senate into chaos and played ducks and drakes with the Turnbull government's legislative agenda.

The Senate mess over Day and Culleton has also highlighted the need for the Solicitor-General, the government's chief legal adviser, to provide frank and fearless advice.

While Prime Minister Malcolm Turnbull attempts to put a positive spin on the unintended disorder his Senate changes have wrought, the future of bills on the same-sex marriage plebiscite and the Australian Building and Construction Commission's resurrection is uncertain until the High Court rules on Day's eligibility to be elected and Culleton's eligibility to remain in the Senate.

When the Senate resumes on Monday, Family First will be nowhere to be seen. And Pauline Hanson seems to have mislaid 25 per cent of her Senate workforce with Culleton's immediate future unclear. To pass bills opposed by Labor and the Greens the Turnbull government will require eight of nine crossbenchers.

Day, a veteran Family First Party Senator from South Australia, resigned after his building companies went bust owing $38 million and it emerged he may have got the taxpayer to rent his electoral office in a building in which he had a financial interest. Further, unions claim a $2 million federal government grant to an Adelaide trade school when Day was chairman of the board was a bid to buy his vote. The conflagration spread further on Friday when a photograph emerged of the Minister of Education and Training, Simon Birmingham, with Day at the school after telling a Senate committee last month he did not recall Day had a role at the college.

Culleton, a new One Nation Senator from Western Australia, is under pressure to resign following his conviction of stealing a $7.50 truck key that may have made him ineligible to stand for election. The conviction was later overturned. Culleton's political credibility has been further eroded by the $6.1 million collapse of his company Elite Grains.

The Senate president on Monday will ask the Upper House to call for a High Court ruling on whether or not Culleton's initial larceny conviction made him ineligible to stand as a candidate. For his part, Culleton joined the chorus of do-gooders in trouble who paint themselves as victims.

"I'm not going to comment on every aspect of my ongoing battle to obtain justice for myself and 4000 other farmers," he said on Thursday, while arguing with the media outside a creditors meeting in Perth.

But in the long view, Day and Culleton have simply pushed their way to front of the crowded trough of privilege, where shameless self-serving and entitlement has swept away older verities of propriety, fair play and doing the right thing.

Few blinked when reports last July alleged Turnbull had forked out $1 million of his own money after his leadership change had deterred corporate donors to Liberal coffers. Andrew Robb, former Trade Minister, Kerry Packer minion and Liberal Party wheeler dealer, this week joined the Landbridge Group, the Chinese company granted a 99-year lease on the Port of Darwin last year.

Turnbull was adamant Robb would adhere to the ministerial code of conduct but the pong lingers, especially as Robb, 65, attracted a lot of sympathy for revealing he suffered from depression and subsequently announced he was bailing out of politics last February to work in mental health and the corporate sector.

The return to Sydney this week of Australia's ambassador to the US, Joe Hockey, also prompted memories of the fortunate life that awaits some who quit politics.

Culleton's achievement in shooting himself in the foot is a reminder of the Brown's cows scenario that befell One Nation in Queensland when the party won 11 seats in the 1998 election only to unravel amid bovine stupidity and petty jealousies.

If Culleton fails to survive, his place will go on the recount to the next candidate on the party's ticket, Peter Georgiou. Felicitously, he is Culleton's brother-in-law.

In South Australia, Family First's future is problematic. Depending on how the High Court rules on whether he was eligible to be elected on July 2, his party could choose Day's successor – his former staffer Rikki Lambert if he wins the High Court case; and if he loses, SA MP Robert Brokenshire or Lucy Gichuhi, the second candidate on the Family First ticket; or the seat could go to Labor.

Day was an Adelaide builder who honed an ultra-conservative mindset into a political career. A member of the H.R. Nicholls Society's board of management from around its 1986 outset, he also pushed for labour market deregulation as founder of Independent Contractors of Australia but, after failing as a federal Liberal candidate in 2007, he fell victim to the party's labyrinthine Adelaide ruling class and jumped ship to Family First. After one electoral mis-step, Day was elected a senator in 2010, a feat he replicated at the federal election in July.

Along the way, for good measure, Day made two loans totalling $405,000 to the Family First Party.

Once in the Senate, Day stood firmly against same-sex marriage, union corruption, was pro-monarchy and anti-climate change but this year his political career self-combusted as his property businesses – Huxley Homes (NSW), Ashford Homes (Victoria), Homestead Homes (SA), Collier Homes (WA) and Newstart Homes (Qld) – collapsed with debts topping $38 million.

Then word got out how Day had flogged a building to a company he loaned money to buy it – and then had the Commonwealth rent space in it for his electoral office. After fiddling around, Day resigned but in his wake left a huge question mark over who would replace him in the Senate.

The saga has thrown into sharp relief the dysfunctional relationship between the country's two top lawyers, Attorney-General Senator George Brandis and Solicitor-General Justin Gleeson, SC.

The constitutional conundrum confronting the government over Day and Culleton is precisely the sort of issue on which the Solicitor-General, the government's chief legal adviser, should provide frank and fearless advice.

Gleeson announced on October 24 that he would resign his post, saying their relationship was "irretrievably broken".

Brandis has come under fire over a legally binding direction he issued before the July election stopping ministers and departments coming to Gleeson directly for legal advice without the written approval of the Attorney-General.

Brandis sought the advice of a private barrister, former Federal Court judge David Jackson, QC, about whether Day was eligible to stand for re-election to the Senate. The advice was received on October 27 and the government now intends to ask the High Court to rule on whether Day was incapable of being elected as a Senator under section 44(v) of the Constitution, which disqualifies people with pecuniary interests in a contract with the Commonwealth from serving in either house of Parliament.

Gleeson himself was asked on October 13, a day before he fronted an explosive Senate inquiry into his stand-off with Brandis, to advise the government on Culleton's eligibility to hold office.

He furnished his opinion on October 28 and the government also wants the High Court to rule on whether Culleton is disqualified from sitting in the Senate because he was convicted of an offence.

The Senate will decide on Monday if both of those matters should be referred to the High Court.